The now-$30,000 reward includes contributions from the Los Angeles County Board of Supervisors, the city of Malibu and the victim's employer.
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Tristan Beaudette was camping with his two young daughters when he was shot in the head last month.
So far, there are no suspects.
Deputies said there have been several other shootings in the area over the last two years.
If you have any relevant information about this ongoing investigation, you're urged to contact the Los Angeles County Sheriff's Department's Homicide Bureau at (323) 890-5500. You can also submit anonymous tips by calling Crime Stoppers at (800) 222-TIPS.