Preston was engaged to Sheen in 1990 when he allegedly shot her in the arm accidentally. The couple broke up shortly after the incident.
During his show yesterday in Vancouver, Sheen said he was drinking coffee in the home he shared with Preston when he heard a shot from upstairs and saw a bloody Preston standing at the top of the staircase, TMZ reported.
Sheen claimed Preston had picked up a pair of his pants – which had a revolver in one of the pockets – from the bathroom floor.
The gun fell out of the pocket and onto the floor and discharged, he said.
He said Preston was not hit with a bullet, but with porcelain shrapnel from the bullet striking the toilet.
Sheen reportedly said he knew at the time that he would be blamed for the incident.
The 18-city My Violent Torpedo of Truth ends today in Seattle.