BOSTON — The bombs that ripped through the crowd at Monday’s Boston Marathon were fashioned out of pressure cookers and packed with metal shards, nails and ball bearings to inflict maximum carnage, a person briefed on the investigation said Tuesday.
And the FBI, which took the lead role in carrying out the investigation into the attack on the annual Patriots Day road race, joined President Obama in confirming that the agency is now probing the twin bombings as a case of domestic or international terrorism.
The two explosive devices — Gov. Deval Patrick and other officials said Tuesday that, contrary to Monday reports, there were no other unexploded devices found along the route or around Boston — had been placed in 6-liter kitchen pressure cookers, hidden in black duffel bags and left on the ground. They were packed with shrapnel, 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 essentially corroborated 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.
Similar pressure-cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 intelligence report by the FBI and Homeland Security. Also, 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.
“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.