Not long after the FBI identified the two suspects thought to be responsible for the bombing at the finish line of the Boston Marathon, one was killed in a gun fight with police, and another remains on the loose.
According to a USA Today report, Boston and its suburbs were locked down Friday as the manhunt intensified for the surviving suspect in the Boston Marathon bombing, hours after the suspect's older brother was killed.
A door-to-door search was underway in Watertown for Dzhokhar Tsarnaev, 19, the brother of the dead suspect, Tamerlan Tsarnaev, 26, law enforcement authorities told USA TODAY.
The brothers are believed to have been in the U.S. for at least a decade, along with other family members, a federal law enforcement official said.
The surviving suspect is believed to be the same man who dropped a backpack laden with explosives at the site of the second explosion. He was pictured wearing a white baseball cap in video images released by the FBI Thursday.