House of Drumming.com

WATERTOWN — The search for one of the Boston Marathon bombing suspects -- the man seen wearing a white baseball cap -- this morning led to the sudden shutdown of the MBTA’s entire network of commuter rail, bus, and subway services.

The other Boston Marathon bombing suspect, the man seen wearing a black hat in photos released Thursday evening, is dead after firing bullets and launching explosives at police.

Boston Police Commissioner Edward F. Davis this morning said the man now known as Marathon bombing Suspect #2 -- seen in photos released Thursday wearing a white baseball cap -- is the person being sought by a massive collection of federal, state, and municipal police. He is believed to be the suspect who actually dropped the bombs at the race finish line.

According to Alben, the night’s outbreak of violence began when police received reports of a robbery of a convenience store in Kendall Square near MIT. A few minutes later, an MIT police officer, who has not been identified, was shot multiple times while in his cruiser at Main and Vassar streets, near Building 32, better known as the renowned the Stata Center on the MIT campus.

The officer was pronounced dead at Massachusetts General Hospital.

A short time later, two men carjacked a Mercedes SUV at gunpoint, and the owner of that car was able to flee at a gas station on Memorial Drive. The SUV proceeded out Memorial Drive toward Watertown followed by a long train of police vehicles in pursuit.

At one point during the pursuit, the two suspects opened fire on Watertown police and a Transit Police officer, who was shot and who is now in critical condition at a Boston-area hospital this morning.

During the gunfight, the man known as Marathon suspect #1 was wounded and was taken into custody. This morning, Dr. Richard Wolfe said the man was brought to the Beth Israel Deaconess Medical Center emergency room around 1:10 a.m. with multiple traumatic injuries.

“It was more than gunshot wounds,’’ Wolfe told reporters around 5:30 a.m. today. “It was a combination of injuries. We believe a combination of of blasts, multiple gunshot wounds.’”

Wolfe said it looked like the man had been hurt by an “explosive device’’ and that the man was struck by “shrapnel.’’

The man was pronounced dead at 1:35 a.m. The hospital said they did not know his name.