Shortly after the MIT officer was shot dead Thursday night, police got a report of a carjacking in Cambridge, just outside Boston. Police were then led on a chase to nearby Watertown.
One of the two suspects in that officer's shooting was killed. Police say of the at-large suspect, "We believe this to be a terrorist, who came here to kill us."
Massachusetts State and Boston Police held a press conference around 4:15 a.m., confirming that the one suspect killed was suspect number one in the Boston Marathon bombings. The second suspect is the man scene in FBI photos in a white baseball cap.
The Middlesex district attorney says the two men are suspected of killing an MIT police officer at the college late Thursday, then stealing a car at gunpoint and later releasing its driver unharmed. Hours earlier, police had released photos of the bombing suspects and asked for the public's help finding them.
After the car chase to the Boston suburb, WCVB in Boston and witnesses on scene reported gunfire and explosive devices being detonated around 1:00 Friday morning in the Watertown area.
Authorities say the suspects threw explosives from the car as police followed it into Watertown. One of the suspects was critically injured during the gunfire and later died, according to State Police.
Massachusetts State police spokesman David Procopio said, "The incident in Watertown did involve what we believe to be explosive devices possibly, potentially, being used against the police officers."
A second police officer, injured during the gunfight, is in critical condition.
Dozens of officers, including National Guard members and the FBI, are now in Watertown.
Massachusetts State and Boston Police are urging everyone to stay inside of their homes, as the area is considered extremely dangerous. They are going door to door, street by street, as a massive manhunt for the second suspect is underway.
FOR LIVE COVERAGE FROM WCVB, CLICK HERE.
This is a fluid situation with ongoing developments. You can count on WPDE NewsChannel 15 to bring you updates as more information becomes available.
The AP contributed to this story.