Two explosions near the finish line of the Boston Marathon on Monday killed three people and injured dozens more. A look at the facts in the case:
Two bombs exploded about 10 seconds and 100 yards apart at about 2:50 p.m. Monday in Boston's Copley Square, near the finish line of the Boston Marathon. An 8-year-old boy, a 29-year-old woman and a Boston University graduate student from China were killed, and more than 170 were injured. The explosions occurred four hours into the race and two hours after the winners had crossed the finish line, but thousands of runners were still on the course.
The bombs consisted of explosives put in common 1.6-gallon pressure cookers, one containing shards of metal and ball bearings, the other packed with nails, according to a person close to the investigation who spoke on condition of anonymity because the investigation was still going on. Both bombs were stuffed into duffel bags, the person said.
Investigators found pieces of black nylon from a bag or backpack and fragments of BBs and nails, possibly contained in a pressure cooker, an FBI agent says. An intelligence bulletin issued to law enforcement and obtained by the AP includes a picture of a mangled pressure cooker and a torn black bag that the FBI says were part of one of the bombs.
The 8-year-old boy killed in the bombings, Martin Richard, was remembered by friends and neighbors as a vivacious boy who loved to run, climb and play sports. Also killed was Krystle Campbell, a 29-year-old restaurant manager from Medford, Mass., whose father, William Campbell, said she had gone with a friend to watch the race.
Boston University said a graduate student was killed. A Hong Kong-based broadcaster said it was a woman from China studying statistics. Her name was not released.
President Barack Obama called the bombings an act of terrorism but said investigators do not know whether they were carried out by an international organization, a domestic group or a "malevolent individual." He said, "The American people refuse to be terrorized."
The area around Copley Square was closed Tuesday, and security was tight around Boston, with bomb-sniffing dogs checking Amtrak passengers' luggage at South Station and transit police patrolling with rifles. The Federal Aviation Administration barred low-flying aircraft within 3.5 miles of the site. Other cities also beefed up security in response to the bombing and the Secret Service expanded its security perimeter around the White House.
Authorities continued to investigate, and DesLauriers said the range of suspects and motives was "wide open." People were asked to come forward with video or photos from the marathon or anything suspicious they might have witnessed, such as hearing someone express an interest in explosives or a desire to attack the marathon, or seeing someone carrying a dark heavy bag at the race.