I don't think the shooter would drive the vehicle into the park, that doesn't seem to make sense if one wants to keep a low profile. There is plenty of room around the park to park a vehicle and walk into the park from what I understand. I tend to think it might be walk able distance to the shooters house (or bike as mentioned).
I thought the trailer park mentioned sounds interesting. It seems like that would be walkable, is close to the Tapia Park area and the campground, and when entering the side street to the temple (with the trailer park right behind it) it would be pretty hidden. It doesn't look like there are any street lights on this side street. It is literally located right after passing the temple. It looks like it has some sort of official recreation and conservation building across the street from it. Any word in Malibu that this blue dude community was to be removed maybe for some park building or maintenance office or something? Something like that could have sparked anger towards the park itself I guess.
Edit: This theory would not address the seasonality of the crimes (assuming they are connected) though since these homes seem to be purchased (and/or rented?) . If somebody was angry about something park related I feel like it would have escalated faster. There would be no reason to wait almost a full year between incidences and then escalate like that. There has to be some sort of seasonal aspect to the shooters locality in this area or his anger or both.