The Boston Marathon bombing suspect was captured Friday night after police found him in a boat in a suburban backyard following a bloody rampage and daylong manhunt, law enforcement sources said. Cheers went up from a crowd of police gathered at the scene in Watertown, Mass., where bursts of gunfire had been heard over the course of two hours. The dramatic turn of events began unfolding soon after police told residents they could leave their homes even though suspect Dzhokhar Tsarnaev, 19, was still on the run. Just before 7 p.m., an unsettling barrage of gunfire was heard on Franklin St. in Watertown, Mass., and dozens of police and armored vehicles sped to the area. Officials said a woman in the area reported seeing blood leading to a boat in her yard, and thermal imaging from helicopters had located someone in the vessel. The capture ended a manhunt that had the city of Boston and its suburbs on total lockdown — following a rampage that included the slaying of a campus security officer, a carjacking and the death of Tsarnaev’s 26-year-old brother, Tamerlan, in a firefight with cops.