A man wearing body armour and armed with an assault rifle shot two Boston police officers who were responding to a report of a domestic disturbance, before being shot and killed by other officers, police said.
The two wounded officers were hospitalised in "extremely critical condition" early Thursday morning (EDT).
"Domestic calls, as you know, are probably the most volatile. You never really know what you're walking into," said Police Commissioner William Evans. "And I think we see right now the dangers of our job."
Evans said the suspect fired at the officers late Wednesday night shortly after they arrived at a home in the city's East Boston neighbourhood. Several other officers who were stationed outside ran inside and exchanged gunfire with the suspect.
"Two of the officers dragged their fellow officers out of the line of fire so they were in a protected zone, and the officers continued to engage in a gun exchange," Evans said.
Police search for a suspect after a police shooting in the East Boston neighbourhood of Boston, Massachusetts.
The officers shot and killed the suspect and then began administering first aid to the wounded officers, one a 28-year veteran, the other a 12-year veteran of the force.
"One officer had his hand in one of the wounds and I think that was instrumental in getting the officer down to Mass General quickly," Evans said.
Both officers were taken to Massachusetts General Hospital, where they were being treated for serious injuries. Nine other officers were being treated at Tufts Medical Center for trauma, stress and minor injuries.
Police, initially concerned that their might be a second suspect, ordered residents to shelter in place. That order was later lifted.
Police did not identify the suspect or the two wounded officers.
As is standard protocol following such events, the district attorney's office said there would be an investigation into the use of deadly force.
"They ran into a firefight here, able to pull two of their officers out safely, and again unfortunately, we had to take a life in doing it," Evans said.
Boston Police Commissioner William Evans told reporters during a press conference early on Thursday that the incident happened on Wednesday night inside an apartment on the city’s east side.
“We had two officer gravely injured there and we had no choice,” he said. “Let’s just hope they pull through.”
Officers were responding to a domestic dispute between two roommates when a man armed with an assault rifle and a protective vest started shooting at them.
The suspect continued firing at officers from an apartment for several minutes, but he was finally shot and killed by other responding officers.
The injured cops are in critical condition. They were taken to Massachusetts General Hospital where they were likely to undergo surgery.
“Please pray for our officers,” the Boston Police Department tweeted after the shooting.
The motive for the shooting and identities of the wounded officers are not yet known.
In another confrontation, one police officer was shot and wounded in Baltimore, Maryland.
He was reportedly recovering in a hospital. Police were searching for three suspects.
The incidents are the latest in a string of fatal shootings of law enforcement officers across America amid an outcry over the deaths of unarmed African Americans at the hands of police.