A man and a woman suspected of taking part in a shooting attack that killed 14 people and wounded 17 at a California social services agency on Wednesday died in a shootout with police hours later, authorities said.

One police officer was injured in the gunfight with the two suspects, who were confronted in their getaway vehicle after fleeing the scene of the shooting in San Bernardino, about 60 miles east of Los Angeles.

Authorities also detained an individual seen running away from the vehicle, but investigators were not immediately sure that person was involved in the case, Police Chief Jarrod Burguan said at a news conference.

The chief added he knew of no possible motive for the shooting spree, which unfolded at 11 a.m. on the campus of the Inland Regional Center, an agency that serves the developmentally disabled.

The shooting rampage marked the deadliest U.S. gun violence since the massacre at Sandy Hook Elementary School in Newtown, Connecticut, in December 2012, in which 27 people, including the gunman, were killed.

The Los Angeles Times, citing information from a senior federal official who was monitoring the case, reported that investigators believe one of the shooters left the party after getting into an argument and returned with one or two armed companions.

The police chief said he was aware that someone left the party following some kind of dispute but did not know whether that individual returned.