BOSTON — 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: Martin Richard, 8, who attended the race with his family, Krystle Campbell, 29, who was waiting to take a picture of her best friend’s boyfriend crossing the finish line, and a Boston University graduate student. The third victim’s name was withheld, pending notification of family.
Officials said 176 runners and onlookers were injured, 17 critically. A massive police investigation was under way 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 two hours before. The second bomb was set off about 100 yards down the street outside the Forum restaurant.
Authorities did not know who planted the bombs. The FBI, which is heading the investigation, said there were no suspects at present.
Investigators were studying surveillance video from security cameras stationed along the marathon course, including the finish line. They also viewed television footage of the race and numerous smartphone video and photos submitted by spectators.
Richard DesLauriers, special FBI agent in charge of the investigation, said “voluminous tips” had been provided to law enforcement officials.