At least two people were killed at Lackland Air Force Base in San Antonio on Friday, the Bexar County Sheriff's Office said.
The sheriff's office had responded to reports of a shooter at the base. Deputies from the county that includes San Antonio were inside the base and the scene was still active, the office said in a tweet.
Parts of the base were placed on lockdown, including three schools, the sheriff's office said. Military police and sheriff's deputies were clearing out buildings.
Authorities also ordered people at a nearby industrial complex to stay in their buildings.