SAN BERNARDINO, Calif. (AP) – The FBI says it is investigating the deadly mass shooting in California as an “act of terrorism.”

David Bowdich, assistant director of the FBI’s Los Angeles office, made the declaration at a news conference Friday in California.

He also said the shooters attempted to destroy evidence, including crushing two cell phones and discarding them in a trash can. He said authorities continue to investigate the case to understand the motivations of the shooters and whether they were planning more attacks.