'I am in shock': Here's what we know about the San Bernardino shooting suspects

Two suspects accused of shooting at least 31 people in San Bernardino on Wednesday - 14 of them fatally - were a couple with a 6-month-old daughter, according to reports and investigators.

San Bernardino Police Chief Jarrod Burguan said investigators were "reasonably confident" that Syed Rizwan Farook, a 28-year-old US citizen, and Tashfeen Malik, 27, were the suspects who opened fire Wednesday on a company event at the Inland Regional Center - a county organization that provides services to the disabled.

Both suspects were killed Wednesday night after a police-car chase Wednesday night.

Police said 17 others were injured in the shooting. A third person who ran away from that scene had been detained, said David Bowdich, the assistant director of the FBI's Los Angeles bureau.

But San Bernardino police say they believe Farook and Malik were the only shooters involved in the Inland Regional Center massacre.

"They came prepared to do what they did as if they were on a mission. They came in with a purpose," Burguan said, noting that the shooters were armed with long guns. "They came in with the intent to do something."

Farook was born in Illinois to Pakistani parents, according to The New York Times, and he had worked at the San Bernardino County health department for five years.

From The Times:

The department held its annual holiday party at the center on Wednesday, which Farook had attended last year as well.

This year, however, Farook apparently left the event "under some circumstances that were described as angry," Burguan, the police chief, said in a press conference. He returned with his wife - and guns - around 11 a.m. local time.

The couple had a 6-month-old baby girl - who they left with Farook's mother the morning before the attack - and appeared to be "living the American dream," one of Farook's coworkers, Patrick Baccari, told the Los Angeles Times.

Farook was described by his colleagues as "quiet and polite," the LA Times reported. They added that he had no "obvious grudges" with any of his coworkers.

"He never struck me as a fanatic, he never struck me as suspicious," Griselda Reisinger, who worked with Farook before leaving the agency in May, told the LA Times.

Farook apparently met his wife of two years online before traveling to Saudi Arabia and returning home with her to California.

Police don't know yet their motive, but the weapons the couple used to stage their attack - and reports that they had stored explosives in the building - suggest a high degree of planning.

Farook and Malik were reportedly armed with four guns: two semiautomatic handguns purchased legally, and two .223-caliber assault rifles.

They were also dressed in tactical gear and had "several mags" full of backup ammunition, Meredith Davis, a spokeswoman at the Bureau of Alcohol, Tobacco, Firearms, and Explosives, told NBC News.

"They were in tactical gear and had several mags full of ammunition fashioned to their body so they were ready for a gunfight should that occur," Davis said.

"With my experiences with other mass shootings, there are indicators this was well-planned out and it was to be violent in nature," Davis added.

Farook's brother-in-law said in a press conference on Wednesday evening that he was "in shock" over the news.

"I have no idea why would he do that," Farhan Khan told reporters. "I have absolutely no idea. I am in shock myself."

This article has been updated to reflect the following correction: A photo of a .223 caliber rifle (AR-15) has replaced the previous image of an AK-47 assault rifle.