The San Diego Chargers are investigating a video that seems to show a stadium security guard masturbating on the sidelines ... just a few feet away from the team's cheerleaders.
The video showed up on Facebook Monday ... the day after the Chargers played the Raiders in San Diego. The clip shows a guy in a red jacket, repeatedly jerking his hand while in the pocket of his pants.
We checked, and the the jacket he's wearing does match up with other guards -- who work for Elite Security -- in Qualcomm Stadium.
The team hasn't identified the guy in the video, but issued a statement saying .