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.
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 responding to an appeal to help provide evidence of what happened.
Richard DesLauriers, special FBI agent in charge of the investigation, said “voluminous tips” had been provided to law enforcement officials, and that efforts were underway to check out every one of them.
"We will go to the ends of the earth to identify the subject or subjects who are responsible for this despicable crime,” said Richard DesLauriers, special agent in charge of the FBI’s Boston office.
The twin explosions occurred more than four hours after the start of the 117th Boston Marathon, and after more than half of the 23,000 runners had completed the race. Police said the explosions happened 12 seconds apart at 2:50 p.m.
Officers sweeping the area screened other suspicious packages in the vicinity, but officials said they did not discover any other explosives. They also said the finish line area had been checked for suspicious objects an hour before the bombs exploded.
Martin Richard, 8, of Boston’s Dorchester neighborhood, was identified as one of the three dead. His mother and 6-year-old sister suffered serious injuries. The father, Bill Richard, said the family had just returned to the finish line area from an ice cream treat when the blast occurred.
“We thank our family and friends, those we know and those we have never met, for their thoughts and prayers,” said the father. “I ask that you continue to pray for my family as we remember Martin.”
Authorities said Krystle Campbell, 29, the manager of a restaurant in nearby Arlington, was also killed as she waited near the finish line to snap a picture of her best friend’s boyfriend, who was running the marathon. The best friend was seriously injured.
William Campbell described his daughter as “very caring, very loving” and “daddy’s little girl.” He said her family was “devastated” by her death.
The third person killed in the bombings was identified by Boston University as a graduate student. The victim’s name was withheld, pending notification of family. The university website BU Today said the student watched the marathon near the finish line with two other students, one of whom was injured and in stable condition at Boston Medical Center Hospital.
Six Boston hospitals treated the injured, several of whom were in critical condition. A doctor at Massachusetts General Hospital, where 30 of the victims were taken, said most of the serious wounds involved burns and lower body extremities.
Dr. George Velmahos, chief of trauma surgery at Mass General, said some patients withstood 40 or more metal pellets, nail-like fragments and other sharp objects that were likely packed into the bombs.
Liz Norden of suburban Wakefield told the Boston Globe that two of her sons, both in their 30s, each had a leg amputated from the knee down.
President Obama, speaking on national television Monday night from the White House, assured the nation “we will find who did this and we will find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice.”
Investigators said they did not know if the bombings were connected in any way to the fact the marathon is always staged on Patriots Day, a state holiday in Massachusetts commemorating the battles of Lexington and Concord that led to the Revolutionary War more than 235 years ago. It was also noted that Monday was the deadline for filing federal tax returns.
The marathon is an iconic Boston event, attracting elite runners from across the world. Lelisa Desisa of Ethiopia won the men’s division Monday, and Rita Jeptoo of Kenya the women’s division. Both finished more than two hours before the bombing.
The London Marathon announced Tuesday it would proceed with that race on Sunday as planned. Sports Minister Hugh Robertson said he was confident of the course’s security. He encouraged spectators to attend as a show of solidarity with the Boston Marathon.
— Details for this story were provided by the FBI, Massachusetts State Police, Boston Police Department and Associated Press.