The first Air Force instructor convicted of rape in a sex scandal at one of the nation's busiest military training centers has died in prison.

Staff Sgt. Luis Walker died at a hospital Sunday night after being found unresponsive two days earlier in his cell at Fort Leavenworth, Kansas.

Prison spokeswoman Denise Haeussler says the cause of death is being investigated.

She says no further details will be available until the Army criminal investigators have completed their work. It's unclear how long that will take.

A military jury in 2012 found Walker guilty of 28 counts, including rape and aggravated sexual assault.

Walker's was the first trial following a scandal in which dozens of instructors from Lackland Air Force Base in San Antonio were accused of preying on female recruits.