The twin killer bombs that exploded seconds apart at the Boston Marathon contained metal pellets, including nails and ball bearings, packed into 6-liter pressure cookers with timers, investigators reported Tuesday.
They said the bombs were hidden inside black duffel bags dropped alongside spectator-crowded Boyleston Street near the 26.2-mile course’s finish line. They said a circuit board recovered at the scene may have been used to remotely detonate the bombs.
The Monday afternoon bomb blasts killed three spectators: an 8-year-old boy who attended the race with his family; a 29-year-old woman who was waiting to take a picture of her best friend’s boyfriend crossing the finish line, and a Boston University graduate student.
Officials said 176 runners and onlookers were injured, 17 critically. A massive police investigation was underway for clues to the who and why of the tragedy.
“This was a heinous and cowardly act,” President Obama said Tuesday.. “And given what we now know about what took place, the FBI is investigating it as an act of terrorism.”
Investigators said the first bomb exploded across from the finish line viewing stands where Massachusetts Gov. Deval Patrick and other dignitaries had been sitting when the first runners finished about two hurs before the blasts. The second bomb was set off about 100 yards down the street outside the Forum restaurant, they said.
Authorities did not know who planted the bombs, how many perpetrators might have been involved or what motived the carnage. The FBI, which is heading the investigation, said there were no suspects at present.
Late Monday night, FBI agents searched the high-rise suburban apartment of a Saudi Arabian student who was burned in the bombings. He was temporarily considered a “person of interest” but the search and further inquiry cleared him of suspicion.
Boston police reduced the sealed crime scene in the heart of Boston from 15 to 12 blocks Tuesday. Police Commissioenr Ed Davis said he would further collapse the blocked-off area in the next few days as the investigation progressed. Bomb-sniffing dogs patroled the streets, alleyways and subway stations.