Boston's police commissioner confirmed early Friday that one of the suspects in this week's deadly bombing attack at the Boston Marathon is dead, while the second remains at large amid a massive manhunt that has paralyzed this northeastern city.

Ed Davis confirmed reports by the local WCVB television station, saying that the slain individual is a man identified by the FBI as "suspect No. 1" in the marathon bombing and who was seen in a surveillance video on the day of the race wearing a black cap and sunglasses.

In a press conference, police said the second suspect, who in other surveillance footage released Thursday was wearing a white cap, is on the loose and is the subject of a manhunt in Watertown, a west Boston suburb.

Shortly before the hunt began for the suspect, Boston police released a photo of the man, identified as Dzhokhar Tsarnaev, a 19-year-old of Chechen origin.

Tsarnaev had lived for at least a year in Cambridge, a Boston suburb that is the home of the world-famous Harvard University and Massachusetts Institute of Technology.

Dzhokhar's brother, 26-year-old Tamerlan, has been identified as the slain suspect.

The huge police operation in Watertown was launched after an MIT campus security officer was killed Thursday night.

He was reportedly slain by the two suspects after responding to a convenience store robbery near central square in the Boston suburb of Cambridge.

The suspects then fled the scene after hijacking a car and headed from Cambridge to Watertown. While being chased by police, they seriously wounded a transit system police force officer.

The pursuit ended in Watertown, where one of the suspects, Tamerlan Tsarnaev, was killed in a shootout with police and his brother fled.

According to CNN, the slain suspect's body may have been strapped with explosives, which would explain why he arrived at the hospital with detonation wounds.

Police have launched a massive deployment of manpower and armored vehicles in the suburb of Watertown; they were taking great precautions for fear the at-large suspect has planted or is carrying explosives.

A pair of bombs went off near the finish line of Monday's Boston Marathon, leaving three dead and more than 140 wounded. EFE