This story has been updated.
Police have identified two people suspected of opening fire at a California social services center Wednesday before being later killed by police.
Syed Farook, 28, and Tashfeen Malik, 27, were killed in a shootout with police more than four hours after the shootings at the Inland Regional Center in San Bernardino that left 14 people dead, San Bernardino Police Chief Jarrod Burguan said.
"I just cannot express how sad I am for what happened today," Farook's brother-in-law, Farhan Khan, said at a press conference held by the Muslim advocacy group the Council on American-Islamic Relations Wednesday night.
"I am in shock that something like this could happen," Khan said. Khan is married to Farook's sister
The shooting at the Inland Regional Center occurred at around 11 a.m. Police said two shooters barged into a conference room during a Christmas party for San Bernardino County employees and opened fire before fleeing in a black sport-utility vehicle.
Farook, a health inspector for the county health department for five years, was at that party.
"He was at the party, he did leave the party under some circumstances that were described as angry," Burguan said. A motive is still undetermined, Burguan said.
Between 10 and 30 minutes passed from when Farook left the party and the shooting, Burguan said.
Explosive devices were found in the center after the shooting, and Farook and Malik were wearing "assault-style clothing" and armed with assault-style rifles when they were killed, Burguan said.
Farook and Malik were in some type of relationship, Burguan said, police were not immediately sure if they were married or if they were boyfriend and girlfriend. Farook was born in the U.S., Burguan said. He couldn't provide more details about Malik.
A person named Syed Farook is listed in public records as a resident of the Redlands address from which police tracked the SUV involved in the afternoon shootout.
That home was surrounded by law enforcement officers Wednesday night. An ATF official said a robot was sent inside to sweep the home for explosives.
Khan said he last spoke with Farook about a week ago. He expressed condolences to the families of those killed and those injured.
"I have no idea why he would do that, why he would do something like this," Khan said. "I am in shock myself."
A motive has not been determined. David Bowdich, assistant director for the FBI's Los Angeles office, said it has not been determined whether the shooting was linked to terrorism, but he said the investigation is in its early stages and "we will go where the evidence takes us."
The ATF said two rifles and two handguns were recovered, and the bureau is conducting "urgent traces" on the weapons.
Two of those weapons were bought legally by someone involved in the investigation, sources familiar with the police investigation told NBC News.
Additional reporting by Andrew Blankstein and Richard Esposito.
This article first appeared on NBCNews.com.