RICHMOND (KPIX 5) — San Francisco police say the suspect who shot and killed himself after a traffic stop in Richmond on Monday was an SFPD officer.

Law enforcement sources tell us the officer was being investigated for sex with a minor in Las Vegas.

Richmond police said on Monday afternoon that they pulled the suspect over in the Hilltop Mall parking lot, near J.C. Penney.

After stopping the vehicle, the responding officer heard a gunshot and called for help.

San Francisco police have not identified the officer yet, but KPIX 5 confirmed that the car is registered to Antonio Cacatian.

The Contra Costa District Attorney’s Office has opened an investigation.