At least two heavily armed attackers opened fire on a banquet at a social services center for the disabled Wednesday, killing 14 people and seriously wounding more than a dozen others in a precision assault that looked "as if they were on a mission," authorities said. About four hours later, police hunting for the killers riddled a black SUV with gunfire in a shootout 2 miles (3 kilometers) 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 who was spotted running near the gun battle was detained, but Burguan said it was unclear if that person had anything to do with the crime. The shooting at the social services center occurred at a holiday celebration for workers, not the disabled. It was the nation's deadliest mass shooting since the attack at a 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 is looking at several possibilities, including workplace violence and terrorism. He did not elaborate. Late Wednesday, a law enforcement official who was briefed on the case identified one of the suspects as Syed Farook. The official was not authorized to speak to the media about the ongoing investigation and spoke to The Associated Press on condition of anonymity. Farhan Khan, who is married to Farook's sister, told reporters he last spoke to his brother-in-law about a week ago. He said he was in shock and had "absolutely no idea why he would do this." The attackers invaded the Inland Regional Center and began shooting around 11 a.m. Wednesday. They opened fire in a conference area that the San Bernardino County Department of Public Health had rented out for an employee banquet, said Marybeth Feild, president and CEO of the nonprofit center. Police spokeswoman Sgt. Vicki Cervantes said witnesses reported seeing one to three gunmen. "They came prepared to do what they did, as if they were on a mission," Burguan, the police chief, said. Burguan 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 (100 kilometers) 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 hospitalized in critical condition, and three were in serious condition, Fire Chief Tom Hannemann said. FBI agents and other law enforcement authorities converged on the center 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 weren't trying to slip out. They had indeed escaped. One witness, Glenn Willwerth, who runs a business across the street, said he heard 10 to 15 shots and 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 blocked 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 gunbattle broke out around 3 p.m., authorities said. One officer suffered 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 center, and during the car chase, the couple hurled a fake bomb — a metal pipe stuffed with cloth — out of the SUV, she said. President Barack Obama was briefed on the attack by his homeland security adviser. He 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," Obama told CBS. According to its web page, the center has a client base of more than 30,000 people with developmental disabilities and their families. It is a privately run nonprofit, the largest of its kind in California with about 670 employees. — AP