A gay man is among the 14 people who were killed on Wednesday in a mass shooting at a California social service center.

The Los Angeles Times reported that Daniel Kaufman, 42, managed the coffee shop in one of the buildings at the Inland Regional Center in San Bernardino. His boyfriend of nearly three years, Ryan Reyes, found out almost 24 hours after the shooting that Kaufman had died.

Authorities say that Syed Farook, an inspector with the San Bernardino County Department of Public Health, and his wife, Tashfeen Malik, opened fire on a holiday party that was taking place inside the social service center. Farook and Malik later died during a shootout with police.

Twenty-one people were injured during the shooting that took place roughly 60 miles east of Los Angeles.

The Associated Press on Thursday cited an official who said the Federal Bureau of Investigation is investigating the shooting as a potential act of terrorism. The massacre is the largest mass shooting to take place in the U.S. since Adam Lanza killed 20 students and six staffers at Sandy Hook Elementary School in Newtown, Conn., in December 2012.