DALLAS – An airman shot his commander in an apparent murder-suicide Friday at a U.S. Air Force base in San Antonio, a senior U.S. official said.

The official spoke on condition of anonymity because he wasn’t authorized to publicly discuss the shooting at Joint Base San Antonio-Lackland.

Two handguns were found near the bodies of the men, which were inside a building that’s used for classrooms and offices, according to Brig. Gen. Robert LaBrutta, who oversees Joint Base San Antonio.

He stressed that the shooting was not an act of terrorism, and declined to identify the two, saying their families must be notified first. The Air Force’s Office of Special Investigations is leading the investigation, and the FBI is assisting.

Military-issued and personal firearms are heavily restricted on the base and it’s not clear whether the gunman was authorized to have a weapon, according to Dan Hawkins, a spokesman for the base.

Weapons are used for training purposes and carried by base security personnel, Hawkins said, but personal firearms cannot be freely carried on the base. He also said security officers must be notified if a personal weapon is being brought onto the installation and the firearm also must be registered, in addition to other requirements.

The fatal shooting of the two is the latest to occur at a military facility in Texas in the last several years.

In January 2015, an Army veteran and former clerk at the veterans’ clinic at Fort Bliss in El Paso shot and killed a psychologist, then killed himself. About a year earlier, three soldiers were killed and 16 wounded in an attack at Fort Hood near Killeen by Army Spc. Ivan A. Lopez, who also killed himself.

And in the deadliest attack to occur at a U.S. military installation, 13 people were killed and 31 were wounded in a mass shooting in 2009 at Fort Hood. Nidal Hasan, a former U.S. Army major, was convicted and sentenced to death in that shooting.

Joint Base San Antonio-Lackland is the home of Air Force basic training. The Army’s Fort Sam Houston and Air Force’s Lackland and Randolph bases were combined during base realignment several years ago to become the military’s largest joint base.

Associated Press writer Lolita C. Baldor in Washington contributed to this report.