Boston remains on lockdown after police conducted a manhunt for two suspects of the Boston Marathon bombings early Friday morning, leaving one of the suspects and a police officer dead. CNN has identified the suspects as brothers Tamerlan Tsarnaev, 26, and Dzhokhar Tsarnaev, 19.FBI releases photos of two people of interest in Boston Marathon bombingsThe older brother, Tamerlan, was shot by police and killed after a car chase through the suburb of Watertown, Mass., in which the suspects reportedly threw explosives at trailing officers.Originally from Chechnya, the brothers moved to the U.S. several years ago. Tamerlan attended Bunker Hill Community College, where he studied engineering.Police have instructed Boston residents to lock their homes and stay away from windows and doors while Dzhokhar remains at large. The subway and Amtrak system has been shut down and every Boston area school is closed. Federal, state and local law enforcement are currently going door-to-door in Watertown, said Massachusetts State Police spokesman Col. Timothy Alben.VIDEO: Stephen Colbert dedicates monologue to Boston Marathon bombingsThe brothers began a crime spree late Thursday night, allegedly robbing a 7/11 convenience store before fatally shooting a Massachusetts Institute of Technology police officer in his car. They proceeded to hijack a car at gunpoint, but released the driver half an hour later at a gas station. According to the district attorney's office, police began pursuing the suspects while they threw explosives out the windows and shot at the officers.Law enforcement fired back, wounding Tamerlan, who later died at Beth Israel Hospital. He reportedly had bullet wounds and injuries from an explosion. A transit system officer was also injured during the incident. His condition remains unknown.