The cause of death was "blunt head and neck trauma," according to the Office of the Chief Medical Examiner for northern Virginia.
"The injuries sustained were consistent with a fall and the death appears to be accidental," said Det. Steve Gomez, a spokesman for the Arlington County Police Department. "We have no evidence of foul play."
It was unclear what precipitated the fall. The medical examiner performed toxicology tests as a part of the autopsy. The results of those tests were not released.
Two of Gillmor's aides discovered his body crumpled at the base of a flight of stairs in his home Wednesday morning after he failed to show up for work. The Ohio Republican was 68.