One of two suspects in the Boston Marathon bombing is dead and a massive manhunt is under way for another, authorities said early Friday.
In a long night of violence the two suspects killed an MIT police officer, injured a transit officer in a firefight, and threw explosive devices at police during their getaway attempt, authorities said.
Boston was in lockdown Friday as the search for the suspect continued. Boston Police Commissioner Edward Davis says the suspect at large is the one seen in the white hat in images of the Boston Marathon suspects released by the FBI Thursday. Davis says he is "armed and dangerous."
Federal sources have told CBS News national security correspondent Bob Orr that officials believe the suspect who is still alive is either wearing an explosive vest, or has explosives with him.
From Watertown to Cambridge, police surrounded various buildings as they searched for Suspect No. 2. Around 8:30 a.m., officers sprinted toward a house in Watertown, and reporters were pushed back more than a block as helicopters buzzed overhead. SWAT teams, FBI agents and armored vehicles assembled at the scene as sharpshooters across the street trained their guns at the house. They left the house around 9:30 a.m., and a few dozen Boston police officers with assault rifles and helmets then filed into the backyard of a red brick building down the street.
A few dozen Boston police officers with assault rifles and helmets then left that house and were filing into the backyard of a red brick building down the street that they raided at around 7 a.m.
"We believe this man to be a terrorist," said Davis.
Police are evacuating residents in Cambridge who lived on the same block as the suspects, going door-to-door telling people to leave. Police told CBS News it is just a precaution, but they have roped off the area and residents are coming out with suitcases.
At one suspect's apartment building, on Norfolk Street in Cambridge, a CBS News producer at the scene witnessed a woman being taken away authorities, being dragged by her arms. It was not known if she was being arrested or resisting being evacuated.
Some time after police evacuated everyone from the premises, police yelled "Fire in the hole," and detonated something.
The Middlesex district attorney said the two men are suspected of killing a Massachusetts Institute of Technology police officer on campus late Thursday, then stealing a car at gunpoint and later releasing its driver unharmed. Hours earlier, police had released photos of the marathon bombing suspects and asked for the public's help finding them.
Authorities say the suspects threw explosives from the car as police followed it into Watertown. The suspects and police exchanged gunfire, and one of the suspects was critically injured and later died while the other escaped.