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.

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

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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.

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