Heavily-armed attackers shot dead after massacring more than a dozen people
At least two heavily-armed attackers who opened fire on a banquet at a California social services centre for the disabled, killing 14 people and seriously wounding more than a dozen others, looked "as if they were on a mission" authorities have said.
About four hours later, police hunting for the killers riddled a black SUV with gunfire in a shoot-out two miles from the late-morning carnage and a man and woman with assault rifles, handguns and "assault-style clothing" were killed.
San Bernardino police chief Jarrod Burguan said a third person spotted running near the gun battle was detained, but it was unclear if they had anything to do with the crime.
The massacre at the Inland Regional Centre in San Bernadino, which happened during a holiday celebration for employees, is America's deadliest mass shooting since the attack at Sandy Hook Elementary School in Newtown, Connecticut, three years ago that left 26 children and adults dead.
Police shed no light on the motive for the massacre. David Bowdich, assistant director of the FBI's Los Angeles office, said the bureau was looking at several possibilities, including workplace violence and terrorism.
A law enforcement official briefed on the case later identified one of the suspects as Syed Farook.
The attackers stormed the Inland Regional Centre and began shooting at around 11am local time. They opened fire in a conference area that the San Bernardino County Department of Public Health had rented out for the employee banquet, Marybeth Feild, president and CEO of the non-profit centre, said.
Witnesses reported seeing one to three gunmen. "They came prepared to do what they did, as if they were on a mission," Mr Burguan said.
He said that someone had left the morning event after "there was some type of dispute" but investigators were not sure whether that had anything to do with the subsequent massacre in the Southern California city of 214,000 people about 60 miles east of Los Angeles.
As gunfire echoed through the large three-building complex, several people locked themselves in their offices, desperately waiting to be rescued by police. Some texted or telephoned their loved ones and whispered to them what was going on.
Ten of the wounded were taken to hospital in a critical condition and three were in a serious condition, fire chief Tom Hannemann said.
FBI agents and other authorities converged on the centre and searched room to room for the attackers. Triage units were set up outside and people were wheeled away on stretchers. Others were marched from the building with their hands up so that police could search them and make sure the attackers were not trying to slip out.
Glenn Willwerth, who runs a business opposite the centre, said he heard 10 to 15 shots then saw an SUV with blacked-out windows pull out "very calmly, very slowly" and drive off.
As the manhunt dragged on, stores, office buildings and schools were locked down in the city, and roads were sealed off.
About four hours later, with police looking for a dark SUV, officers staking out a home in the nearby city of Redlands saw a vehicle matching that description leave. They pursued the vehicle, the SUV crashed, and a gun battle broke out at around 3pm. One officer received a minor injury.
The aftermath of the shootout was captured live by television news helicopters.
Each of the dead had a rifle and handgun and was wearing tactical clothing, including vests stuffed with ammunition magazines, said Agent Meredith Davis of the Bureau of Alcohol, Tobacco, Firearms and Explosives.
An explosive device was found at the social service centre and during the car chase the couple hurled a fake bomb - a metal pipe stuffed with cloth - out of the SUV, she said.
US president Barack Obama said it was too early to know the shooters' motives but urged the country to take steps to reduce mass shootings, including stricter gun laws and stronger background checks.
"The one thing we do know is that we have a pattern now of mass shootings in this country that has no parallel anywhere else in the world, and there's some steps we could take, not to eliminate every one of these mass shootings, but to improve the odds that they don't happen as frequently," he told CBS.
The brother-in-law of Syed Farook said he was stunned to hear of his involvement in the shooting.
Farhan Khan, who is married to the sister of Farook, spoke at a news conference at the Anaheim office of the Council on American-Islamic Relations.
Mr Khan said he last spoke to Farook about a week ago and added that he had "absolutely no idea why he would do this. I am shocked myself".
He said other family members asked him to speak at the press conference and to express their sadness over the shootings.