One of the Boston Marathon bombing suspects has been shot dead by police in a late night police chase and shootout. The second suspect is still on the run, according to police sources early Friday morning.
One police officer was killed and another seriously wounded during the violent encounter as authorities closed in on the bombing suspects.
At sunrise, Gov. Deval Patrick ordered a shutdown of all public transit in Boston, and residents on the fringes of Boston were ordered to stay indoors as a massive manhunt for the second suspect expanded.
"This is situation is grave and we are trying to protect the public safety," said Massachusetts State Police Col. Timothy Alben, who ordered a temporary lockdown of Watertown, Waltham, Belmont, Cambridge, Newton, Allston and Brighton.
FBI agents were seen in Watertown after local police were involved in a frantic car chase and shootout after authorities released images of the suspects earlier on Thursday.
During the pursuit, officers could be heard on police radio traffic describing the men as having handguns, grenades and other explosives.
It has been reported that at approximately 10.20 p.m. ET on Thursday police were called to a 7-Eleven store in Cambridge after the bombing suspects robbed the store.
Minutes later the men shot and killed an MIT campus officer responding to the robbery call, resulting in a lockdown at the university campus.
The terror suspects then carjacked a Mercedes-Benz with the driver still inside and fled. They later released the driver, but were spotted in Watertown where they exchanged gunfire with patrol officers.
Police are said to have shot and apprehended Suspect 1, who was then rushed to Beth Israel Medical Center. He arrived at the hospital under cardiac arrest with multiple gunshot wounds and blast-like injuries to his chest.
The second suspect fled on foot, leading to a tense manhunt that is still underway early Friday morning.
"We believe this to be a terrorist," said Boston police Commissioner Ed Davis. "We believe this to be a man who has come here to kill people. We need to get him into custody."
According to Boston police, the suspect who remained at large was the "one in the white hat" who was seen in the photos released by the FBI earlier on Thursday.
Locals in Watertown, which is a suburb about 10 miles from downtown Boston, were ordered to stay indoors, and also to turn off their cell phones as fears emerged that improvised explosive devices being used by the suspect could be triggered by the mobile phones.
Police officers frantically searched backyards in search of the second suspect, and a police perimeter of several blocks was established.
K9 units and SWAT teams were also in the process of searching homes, and officers with a police robot searched an SUV that the suspects had abandoned. Reports also emerged that the suspects had left multiple devices in the road and two handguns were recovered.
In a further development, reports released by The Associated Press early Friday described the two suspects as brothers.
Here is a video news report on the killing of Suspect No. 1: