FBI focuses on how Boston bombing carried out with pressure cookers, nails

This image from a Federal Bureau of Investigation and Department of Homeland Security joint bulletin issued to law enforcement and obtained by The Associated Press, shows the remains of a black backpack that the FBI says contained one of the bombs that exploded during the Boston Marathon. The FBI says it has evidence that indicates one of the bombs that exploded in the Boston Marathon was contained in a pressure cooker with nails and ball bearings, and it was hidden in a backpack. (AP Photo/FBI)

This image from a Federal Bureau of Investigation and Department of Homeland Security joint bulletin issued to law enforcement and obtained by The Associated Press, shows the remains of a black backpack that the FBI says contained one of the bombs that exploded during the Boston Marathon. The FBI says it has evidence that indicates one of the bombs that exploded in the Boston Marathon was contained in a pressure cooker with nails and ball bearings, and it was hidden in a backpack. (AP Photo/FBI)

This image from a Federal Bureau of Investigation and Department of Homeland Security joint bulletin issued to law enforcement and obtained by The Associated Press, shows the remains of a pressure cooker that the FBI says was part of one of the bombs that exploded during the Boston Marathon. The FBI says it has evidence that indicates one of the bombs was contained in a pressure cooker with nails and ball bearings, and it was hidden in a backpack. (AP Photo/FBI)

This image from a Federal Bureau of Investigation and Department of Homeland Security joint bulletin issued to law enforcement and obtained by The Associated Press, shows the remains of a pressure cooker that the FBI says was part of one of the bombs that exploded during the Boston Marathon. The FBI says it has evidence that indicates one of the bombs was contained in a pressure cooker with nails and ball bearings, and it was hidden in a backpack. (AP Photo/FBI)

This undated photo provided by the family shows Krystle Campbell. Campbell, 29, a restaurant manager from Medford, Mass., was among the people killed in the explosions at the finish line of the Boston Marathon, Monday, April 15, 2013, in Boston. (AP Photo/Campbell Family)

This undated photo provided by the family shows Krystle Campbell. Campbell, 29, a restaurant manager from Medford, Mass., was among the people killed in the explosions at the finish line of the Boston Marathon, Monday, April 15, 2013, in Boston. (AP Photo/Campbell Family)

This undated photo provided by Bill Richard shows his son, Martin Richard, in Boston. Martin Richard, 8, was among the at least three people killed in the explosions at the finish line of the Boston Marathon Monday, April 15, 2013. (AP Photo/Bill Richard)

This undated photo provided by Bill Richard shows his son, Martin Richard, in Boston. Martin Richard, 8, was among the at least three people killed in the explosions at the finish line of the Boston Marathon Monday, April 15, 2013. (AP Photo/Bill Richard)

— Federal agents zeroed in Tuesday on how the Boston Marathon bombing was carried out — with kitchen pressure cookers packed with explosives, nails and other lethal shrapnel — but said they still didn't know who did it and why.

An intelligence bulletin issued to law enforcement and released late Tuesday included a picture of a mangled pressure cooker and a torn black bag the FBI said were part of a bomb.

The FBI and other law enforcement agencies repeatedly pleaded for members of the public to come forward with photos, videos or anything suspicious they might have seen or heard.

"The range of suspects and motives remains wide open," Richard DesLauriers, FBI agent in charge in Boston, said at a news conference. He vowed to "go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime."

President Barack Obama branded the attack an act of terrorism but said officials don't know "whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual."

Scores of victims remained in hospitals, many with grievous injuries, a day after the twin explosions near the marathon's finish line killed three people, wounded more than 170 and reawakened fears of terrorism. A 9-year-old girl and 10-year-old boy were among 17 victims listed in critical condition.

Heightening jitters in Washington, where security already had been tightened after the bombing, a letter addressed to a senator and poisoned with ricin or a similarly toxic substance was intercepted at a mail facility outside the capital, lawmakers said.

There was no immediate indication the episode was related to the Boston attack. Senate Majority Leader Harry Reid said the letter was sent to Republican Sen. Roger Wicker, of Mississippi.

Officials found that the bombs in Boston consisted of explosives put in ordinary 1.6-gallon pressure cookers, one with shards of metal and ball bearings, the other with nails, according to a person close to the investigation who spoke on condition of anonymity because the probe was still going on. The bombs were stuffed into black duffel bags and left on the ground, the person said.

DesLauriers confirmed that investigators had found pieces of black nylon from a bag or backpack and fragments of BBs and nails, possibly contained in a pressure cooker. He said the items were sent to the FBI laboratory at Quantico, Va., for analysis.

The FBI said it is looking at what Boston television station WHDH said are photos sent by a viewer that show the scene right before and after the bombs went off. The photo shows something next to a mailbox that appears to be a bag, but it's unclear what the significance is.

"We're taking a look at hundreds of photos, and that's one of them," FBI spokesman Jason Pack said.

Investigators said they haven't determined what was used to set off the explosives.

Pressure cooker explosives have been used in international terrorism and have been recommended for lone-wolf operatives by al-Qaida's branch in Yemen.

But information on how to make the bombs is readily found online, and U.S. officials said Americans should not rush to judgment in linking the attack to overseas terrorists.

DesLauriers said there had been no claim of responsibility for the attack.

He urged people to come forward with anything suspicious, such as hearing someone express an interest in explosives or a desire to attack the marathon, seeing someone carrying a dark heavy bag at the race or hearing mysterious explosions recently.

"Someone knows who did this," the FBI agent said.

The bombs exploded 10 or more seconds apart, tearing off victims' limbs and spattering streets with blood, instantly turning the festive race into a hellish scene of confusion, horror and heroics.

The blasts killed 8-year-old Martin Richard, of Boston, 29-year-old Krystle Campbell, of Medford, and a third victim, identified only as a graduate student at Boston University.

Doctors who treated the wounded corroborated reports that the bombs were packed with shrapnel intended to cause mayhem.

"We've removed BBs, and we've removed nails from kids. One of the sickest things for me was just to see nails sticking out of a little girl's body," said Dr. David Mooney, director of the trauma center at Boston Children's Hospital.

At Massachusetts General Hospital, all four amputations performed there were above the knee, with no hope of saving more of the legs, said Dr. George Velmahos, chief of trauma surgery.

"It wasn't a hard decision to make," he said. "We just completed the ugly job that the bomb did."

Obama plans to visit Boston on Thursday to attend an interfaith service in honor of the victims. He has traveled four times to cities reeling from mass violence, most recently in December after the schoolhouse shooting in Newtown, Conn.

In the wake of the attack, security was stepped up around the White House and across the country. Police massed at federal buildings and transit centers in the nation's capital, critical response teams deployed in New York City and security officers with bomb-sniffing dogs spread through Chicago's Union Station.

Homeland Security Secretary Janet Napolitano said that the stepped-up security was a precaution and that there was no evidence the bombings were part of a wider plot.

Pressure cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 intelligence report by the FBI and the Department of Homeland Security. One of the three devices used in the May 2010 Times Square attempted bombing was a pressure cooker, the report said.

"Placed carefully, such devices provide little or no indication of an impending attack," the report said.

The Pakistani Taliban, which claimed responsibility for the 2010 attempt in Times Square, has denied any part in the Boston Marathon attack.

Al-Qaida's branch in Yemen gave a detailed description of how to make a bomb using a pressure cooker in a 2010 issue of Inspire, its English-language online publication aimed at would-be terrorists acting alone.

In a chapter titled "Make a bomb in the kitchen of your mom," it says "the pressurized cooker is the most effective method" for making a simple bomb, and it provides directions.

The tightly sealed pot makes easier-to-obtain but weaker explosives faster and stronger, amplifying the blast and the carnage.

Naser Jason Abdo, a former U.S. soldier, was sentenced to life in prison last year after being convicted of planning to use a pair of bombs made from pressure cookers in an attack on a Texas restaurant frequented by soldiers from Fort Hood. He was found with the Inspire article.

Investigators in the Boston bombing also are combing surveillance tapes from businesses around the finish line and asking travelers at Logan Airport to share any photos or video that might help.

"This is probably one of the most photographed areas in the country yesterday," said Boston police Commissioner Edward Davis. He said two security sweeps of the marathon route had been conducted before the bombing.

Boston police and firefighter unions announced a $50,000 reward for information leading to arrests.

Posted earlier

The bombs that ripped through the Boston Marathon crowd appear to have been fashioned out of ordinary kitchen pressure cookers, packed with nails and other fiendishly lethal shrapnel, and hidden in duffel bags left on the ground, investigators and others close to the case said Tuesday.

President Barack Obama branded the attack an act of terrorism, whether carried out by a solo bomber or group, and the FBI vowed to "go to the ends of the Earth" to find out who did it.

Scores of victims remained in Boston hospitals, many with grievous injuries, a day after the twin explosions near the marathon's finish line killed three people, wounded more than 170 and reawakened fears of terrorism. A 9-year-old girl and 10-year-old boy were among 17 victims listed in critical condition.

Officials found that the bombs consisted of explosives put in common 1.6-gallon pressure cookers, one containing shards of metal and ball bearings, the other packed with nails, according to a person close to the investigation who spoke on condition of anonymity because the investigation was still going on. Both bombs were stuffed into duffel bags, the person said.

At a news conference, FBI agent Richard DesLauriers, FBI agent in charge in Boston, confirmed that investigators had found pieces of black nylon from a bag or backpack and fragments of BBs and nails, possibly contained in a pressure cooker. He said the items were sent to the FBI for analysis at Quantico, Va.

Pressure-cooker explosives have been used in international terrorism, and have been recommended for lone-wolf operatives by Al-Qaida's branch in Yemen. But information on how to make the bombs is readily found online, and U.S. officials said Americans should not rush to judgment in linking the attack to overseas terrorists.

DesLauriers said that there had been no claim of responsibility for the attack, and that the range of suspects and motives was "wide open."

Throughout the day, he and other law enforcement authorities asked members of the public to come forward with any video or photos from the marathon or anything suspicious they might have witnessed, such as hearing someone express an interest in explosives or a desire to attack the marathon, or seeing someone carrying a dark heavy bag at the race.

"Someone knows who did this," the FBI agent said.

The bombs exploded 10 or more seconds apart, tearing off victims' limbs and spattering streets with blood, instantly turning the festive race into a hellish scene of confusion, horror and heroics.

The blasts killed 8-year-old Martin Richard of Boston, 29-year-old Krystle Campbell of Medford, Mass., and a third victim, identified only as a graduate student at Boston University.

Doctors who treated the wounded corroborated reports that the bombs were packed with shrapnel intended to cause mayhem.

"We've removed BBs and we've removed nails from kids. One of the sickest things for me was just to see nails sticking out of a little girl's body," said Dr. David Mooney, director of the trauma center at Boston Children's Hospital.

At Massachusetts General Hospital, all four amputations performed there were above the knee, with no hope of saving more of the legs, said Dr. George Velmahos, chief of trauma surgery.

"It wasn't a hard decision to make," he said. "We just completed the ugly job that the bomb did."

Obama plans to visit Boston on Thursday to attend an interfaith service in honor of the victims. He has traveled four times to cities reeling from mass violence, most recently in December after the schoolhouse shooting in Newtown, Conn.

In the wake of the attack, security was stepped up around the White House and across the country. Police massed at federal buildings and transit centers in the nation's capital, critical response teams deployed in New York City, and security officers with bomb-sniffing dogs spread through Chicago's Union Station.

Homeland Security Secretary Janet Napolitano urged Americans "to be vigilant and to listen to directions from state and local officials." But she said there was no evidence the bombings were part of a wider plot.

Pressure-cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 intelligence report by the FBI and the Homeland Security Department. One of the three devices used in the May 2010 Times Square attempted bombing was a pressure cooker, the report said.

"Placed carefully, such devices provide little or no indication of an impending attack," the report said.

Investigators said they have not yet determined what was used to set off the Boston explosives. Typically, these bombs have an initiator, switch and explosive charge, according to a 2004 warning from Homeland Security.

"We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice," the FBI's DesLauriers said.

The Pakistani Taliban, which claimed responsibility for the 2010 attempt in Times Square, has denied any part in the Boston Marathon attack.

Al-Qaida's branch in Yemen gave a detailed description of how to make a bomb using a pressure cooker in a 2010 issue of Inspire, its English-language online publication aimed at would-be terrorists acting alone.

In a chapter titled "Make a bomb in the kitchen of your mom," it says "the pressurized cooker is the most effective method" for making a simple bomb, and it provides directions.

Naser Jason Abdo, a former U.S. soldier, was sentenced to life in prison last year after being convicted of planning to use a pair of bombs made from pressure cookers in an attack on a Texas restaurant frequented by soldiers from nearby Fort Hood. He was found with the Inspire article.

Investigators are also combing surveillance tapes from businesses around the finish line and asking travelers at Boston's Logan Airport to share any photos or video that might help.

"This is probably one of the most photographed areas in the country yesterday," said Boston Police Commissioner Edward Davis. He said two security sweeps of the marathon route had been conducted before the bombing.

Boston police and firefighter unions announced a $50,000 reward for information leading to arrests.

Obama said officials do not know who carried out the attack or why — "whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual."

But he said "any time bombs are used to target innocent civilians, it is an act of terror." And he declared: "The American people refuse to be terrorized."

Posted earlier

The two bombs that ripped through the crowds at the Boston Marathon, killing three people and wounding more than 170, were fashioned out of pressure cookers and packed with shards of metal, nails and ball bearings, a person briefed on the investigation said Tuesday.

The details on the apparently crude but deadly explosives emerged as investigators appealed to the public for amateur video and photos that might yield clues, and the chief FBI agent in Boston vowed "we will go to the ends of the Earth" to find those responsible.

A person who spoke on the condition of anonymity because the investigation was still going on said that the explosives were put in 6-liter pressure cookers, placed in black duffel bags and left on the ground. They were packed with shrapnel to inflict maximum carnage, the person said.

The person said law enforcement officials have some of the bomb components but do not yet know what was used to set off the explosives.

A doctor treating the wounded appeared to corroborate the person's account, saying one of the victims was maimed by what looked like ball bearings or BBs. Doctors also said they removed a host of sharp objects from the victims, including nails that were sticking out of one little girl's body.

At the White House, meanwhile, President Barack Obama said that the bombings were an act of terrorism but that investigators do not know if they were carried out by an international organization, domestic group or a "malevolent individual."

He added: "The American people refuse to be terrorized."

Across the U.S., from Washington to Los Angeles, police tightened security, monitoring landmarks, government buildings, transit hubs and sporting events. Security was especially tight in Boston, with bomb-sniffing dogs checking Amtrak passengers' luggage at South Station and transit police patrolling with rifles.

"They can give me a cavity search right now and I'd be perfectly happy," said Daniel Wood, a video producer from New York City who was waiting for a train.

Similar pressure-cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 joint FBI and Homeland Security intelligence report. Also, one of the three devices used in the May 2010 Times Square attempted bombing was a pressure cooker, the intelligence report said.

"Placed carefully, such devices provide little or no indication of an impending attack," the report said.

The Pakistani Taliban, which claimed responsibility for the 2010 attempt in Times Square, has denied any role in the Boston Marathon attack.

The two bombs blew up about 10 seconds and around 100 yards apart Monday near the finish line of the storied, 26.2-mile race, tearing off limbs, knocking people off their feet and leaving the streets spattered with blood and strewn with broken glass. The dead included an 8-year-old boy.

"We started grabbing tourniquets and started tying legs. A lot of people amputated," said Roupen Bastajian, a state trooper from Smithfield, R.I., who had just finished the race when he heard the explosions.

Federal investigators said no one had claimed responsibility for the bombings, which took place on one of the city's biggest civic holidays, Patriots Day.

"We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice," said Richard DesLauriers, FBI agent in charge in Boston.

He said investigators had received "voluminous tips" and were interviewing witnesses and analyzing the crime scene.

Gov. Deval Patrick said that contrary to earlier reports, no unexploded bombs were found. He said the only explosives were the ones that went off.

FBI agents searched an apartment in the Boston suburb of Revere overnight, and investigators were seen leaving with brown paper bags, plastic trash bags and a duffel bag. But it was unclear whether the tenant had anything to do with the attack.

A law enforcement official who spoke on condition of anonymity because he was not authorized to release details of the investigation said the man had been tackled by a bystander, then police, as he ran from the scene of the explosions.

But he said it is possible the man was simply running away to protect himself from the blast, as many others did.

At a news conference, police and federal agents repeatedly appealed for any video, audio and photos taken by marathon spectators, even images that people might not think are significant.

"There has to be hundreds, if not thousands, of photos and videos" that might help investigators, state police Col. Timothy Alben said.

Boston Police Commissioner Edward Davis said investigators also gathered a large number of surveillance tapes from businesses in the area and intend to go through the video frame by frame.

"This is probably one of the most photographed areas in the country yesterday," he said.

At least 17 people were critically injured, police said. At least eight children were being treated at hospitals. In addition to losing limbs, victims suffered broken bones, shrapnel wounds and ruptured eardrums.

Dr. Stephen Epstein of the emergency medicine department at Beth Israel Deaconess Medical Center said he saw an X-ray of one victim's leg that had "what appears to be small, uniform, round objects throughout it — similar in the appearance to BBs."

Eight-year-old Martin Richard was among the dead, said U.S. Rep. Stephen Lynch, a family friend. The boy's mother, Denise, and 6-year-old sister, Jane, were badly injured. His brother and father were also watching the race but were not hurt.

A candle burned on the stoop of the family's single-family home in the city's Dorchester section Tuesday, and the word "Peace" was written in chalk on the front walk.

Neighbor Betty Delorey said Martin loved to climb the neighborhood trees, and hop the fence outside his home.

The Boston Marathon is one of the world's oldest and most prestigious races and about 23,000 runners participated. Most of them had crossed the finish line by the time the bombs exploded, but thousands more were still completing the course.

The attack may have been timed for maximum bloodshed: The four-hour mark is typically a crowded time near the finish line because of the slow-but-steady recreational runners completing the race and because of all the friends and relatives clustered around to cheer them on.

Davis, the police commissioner, said authorities had received "no specific intelligence that anything was going to happen" at the race. On Tuesday, he said that two security sweeps of the route had been conducted before the marathon.

The race winds up near Copley Square, not far from the landmark Prudential Center and the Boston Public Library. It is held on Patriots Day, which commemorates the first battles of the American Revolution, at Concord and Lexington in 1775.

Richard Barrett, the former U.N. coordinator for an al-Qaida and Taliban monitoring team who has also worked for British intelligence, said the relatively small size of the devices in Boston and the timing of the blasts suggest a domestic attack rather than an al-Qaida-inspired one.

"This happened on Patriots Day — it is also the day Americans are supposed to have their taxes in — and Boston is quite a symbolic city," said Barrett, now senior director at the Qatar International Academy for Security Studies.

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