Raja Jackson , the son of former UFC light heavyweight champion Quinton "Rampage" Jackson , is in the crosshairs of the LAPD ... after brutally attacking an unconscious wrestling opponent.

The LAPD tells TMZ ... cops were called to the wrestling event Saturday night and took a police report ... and now the incident is being investigated. Play video content

As we reported ... video shows Raja pummeling his KO'd competitor , Syko Stu , at a private wrestling event at KnokX Pro Academy in Los Angeles.

The vicious beatdown sent Syko Stu to the hospital, where an insider told us he was "fine and recovering" as of Saturday night. Kick/Rajaplus

A source close to the event tells TMZ they can "guarantee" Raja will never again be allowed at KnokX Pro wrestling match following what

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