WATERTOWN, Mass. —
The bombings on Monday killed three people and wounded more than 180 others, tearing off limbs in a spray of shrapnel and instantly raising the specter of another terrorist attack on U.S. soil.
Authorities have shed no light on the motive for the attack and have said it is unclear whether it was the work of domestic or international terrorists or someone else entirely with an unknown agenda.
The endgame — at least for Suspect No. 1 — came just hours after the FBI released photos and video of the two young men at the finish line and appealed to the public for help in identifying and capturing them. Tips came pouring in to the FBI immediately, but exactly how authorities managed to close in on the two was not immediately disclosed.
The men's uncle, Ruslan Tsarni of Montgomery Village, Md., told The Associated Press that the men traveled here together from the Russian region near Chechnya.
Their father, Anzor Tsarnaev, said in a telephone interview with The Associated Press from the Russian city of Makhachkala that his younger son, Dzhokhar, is "a true angel."
"Dzhokhar is a second-year medical student in the U.S. He is such an intelligent boy. We expected him to come on holidays here," the father said.
The White House said President Barack Obama was being briefed on developments overnight by Lisa Monaco, his assistant for homeland security and counterterrorism.
The images released by the FBI depict the two young men walking one behind the other near the finish line. Richard DesLauriers, FBI agent in charge in Boston, said Suspect No. 2 in the white hat was seen setting down a bag at the site of the second of two deadly explosions.
Authorities said surveillance tape recorded late Thursday showed Suspect No. 2 during a robbery of a convenience store in Cambridge, near the campus of MIT, where a university police officer was shot to death while responding to a report of a disturbance, said State Police Col Timothy Alben.