Air Force Technical Sgt. Steven D. Bellino served as a special agent for less than two years and left the bureau in May 2013, the FBI said in a statement.
Bellino shot and killed Lt. Col. William A. Schroeder, Bellino's commanding officer in the 342nd Training Squadron at Joint Base San Antonio-Lackland
, before killing himself on Friday morning, an Air Force official told CNN on Saturday. The facility is best known as Lackland Air Force Base.
The men were found dead inside an office at the training squadron headquarters, the release said. Two Glock pistols were found.
James Keith, spokesman for the Bexar County Sheriff's Office, told CNN the killings were a murder-suicide.
No motive has been offered and no details have been released on the relationship, if any, between the two men. The press release referred to the incident as "workplace violence." The sheriff's office said in a tweet that the investigation has been passed to Lackland authorities and federal investigators.
Air Force Times
, citing information from the Air Force, reported that Bellino was 41 and from Parma Heights, Ohio. He'd been a pararescueman student since becoming an active-duty member of the Air Force in June 2015, Air Force Times said.
Schroeder, 39, came from Ames, Iowa, and had been commander of the squadron since May 2014, Air Force Times said. He joined the Air Force in 1999 and had earned several medals, including a Bronze Star.
After the shooting was reported to 911, security personnel evacuated Forbes Hall and initiated a lockdown of the base. They searched the building for about an hour before declaring the situation over.
Lackland is where the U.S. Air Force conducts its basic training for enlistees. Lackland is one of three major military facilities -- the others being Randolph Air Force Base and the U.S. Army's Fort Sam Houston -- that merged to form Joint Base San Antonio in 2010.
"The 37th Training Wing mourns the loss of our Airmen and family members," said Brig. Gen. Trent H. Edwards, commander of the 37th Training Wing, where both members were assigned. "Our primary focus at this time is to take care of the family and the men and women who are grieving our losses."