Law enforcement officials stand behind a police line near the site of the San Bernardino mass shooting. (Whitney Ashton/Annenberg Media)

The FBI announced Friday that it is officially investigating the mass shooting in San Bernardino as an "act of terrorism." 

The names of the fourteen people who were killed in Tuesday’s mass shooting were released Thursday afternoon. The victims’ were from Southern California and ranged in age from 26 to 50.

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Authorities worked overnight to piece together the events leading up to an alleged dispute at a holiday party that resulted in a deadly massacre at the Inland Regional Center in San Bernardino.

Fourteen people were killed and 21 were wounded, making this the deadliest shooting in the U.S. since Sandy Hook in 2012.

Twenty-eight-year-old Syed Farook, an employee of the San Bernardino County public health agency, and his wife Tashfeen Malik, 27, walked into a holiday party held in a conference room and started shooting, police say.

“They sprayed the room with bullets,” San Bernardino Police Chief Jarrod Burguan said.

A bouquet of flowers sits behind police tape near the scene of a shooting rampage in San Bernardino. (Whitney Ashton/Annenberg Media)

While authorities have identified the couple who carried out the shooting rampage, police say their motive remains a mystery.

“We do not yet know the motive,” said David Bowdich, the assistant director of the FBI’s Los Angeles field office. “There was obviously a mission … we do not know why.”

Farook attended the party earlier in the day, but left, possibly due to a dispute, police said.

Malik came to the U.S. with Farook in July 2014 on a work visa and had a Pakistani passport. The two met online and married after arriving in the U.S. They had a six-month-old daughter together.

READ MORE: At Least 14 Victims And 2 Suspects Dead After San Bernardino Mass Shooting

The shooting occurred around 11 a.m. Tuesday and sparked a manhunt that ended in a pursuit and shootout with police hours later. Police received tips that led them to a home in Redlands, Burguan said. Farook and Malik fled in an SUV as officers approached the home. Police gave chase and the pursuit ended in San Bernardino where a gun battle occurred. The two armed suspects were killed. An officer was wounded in the shooting, but his injuries are not believed to be life threatening.

Agents from the L.A. field office of the Bureau of Alcohol, Tobacco, Firearms and Explosives, along with the FBI and the Department of Homeland Security assisted the San Bernardino police and sheriff’s departments in the investigation.

The sheriff’s department says the couple was equipped and could have committed another shooting, but authorities intercepted them before that.

"There were another 2,000 nine-millimeter rounds found at that house, over 2,500 223 rounds, and there were several hundred long rifle rounds that were found [inside the couple’s rented Redlands home]," Burguan said.

“The fact-finding process takes time,” Bowdich said.

A candlelight vigil in San Bernardino and a prayer vigil in Chino were held around 6 p.m. Thursday.

“We will survive this,” Burguan said. 

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