The Los Angeles Board of Supervisors is offering $10,000, and the city of Malibu is offering $5,000.
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Tristan Beaudette, 35, was camping with his two young daughters when he was shot in the head.
No suspects have been named. There have been reports of previous shootings at the same park.
Investigators said they are aware of the other shooting reports, but they said there is no evidence to connect them at this time.