FBI agents yesterday zeroed in 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 did not know who did it or why.
An intelligence bulletin issued to law enforcement and released late on Tuesday included a picture of a mangled pressure cooker and a torn black bag the FBI says were part of a bomb.
The FBI and other prominent law enforcement agencies repeatedly pleaded for members of the public to come forward with photographs, videos or anything suspicious they might have seen or heard.
US President Barack Obama branded the attack an act of terrorism, but said officials do not know “whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual.”
FBI agent Richard DesLauriers said at a press conference that the “range of suspects and motives remains wide open.”
He vowed to “go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime.”
Scores of victims of the Boston bombing remained in hospitals, many with grievous injuries, two days after the twin explosions near the marathon’s finish line killed three people, wounded more than 170.
A nine-year-old girl and 10-year-old boy were among 17 victims listed in critical condition.
Officials found that the bombs in Boston consisted of explosives put in ordinary, 6 liter 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 ongoing.
Both 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 ball bearings and nails, possibly contained in a pressure cooker. He said the items were sent to the FBI laboratory at Quantico, Virginia, for analysis.
Investigators said they have not yet determined what was used to set off the explosives.
The blasts killed eight-year-old Martin Richard of Boston and 29-year-old Krystle Campbell of Medford, Massachusetts. The Shenyang Evening News, a state-run Chinese newspaper, identified the third victim as Lu Lingzi (呂令子) from the northeastern Chinese city.
Doctors who treated the wounded corroborated reports that the bombs were packed with shrapnel.
“One of the sickest things for me was just to see nails sticking out of a little girl’s body,” said David Mooney, director of the trauma center at Boston Children’s Hospital.