Naval Air Station (NAS) Pensacola is on lockdown after law enforcement received a bomb threat Wednesday morning, according to WEAR in Pensacola.

The threat was called in to the Escambia County Sheriff’s Office about 10 a.m. Wednesday, which marks the fourth anniversary of a terrorist attack in which an armed gunman, a Saudi Arabian student, opened fire on the Naval base, killing three and injuring eight others.

The ECSO is not responding to the call, the TV outlet reported, but said it would assist if needed.

NAS Pensacola officials said the base gates are closed and Naval Security is investigating.

Additional details were not immediately available.