I think the best thing you can do is prepare yourself mentally and physically in case a situation arises. You cannot control people shooting at you or anyone else around you, but you can at least take self-defense classes.

I am a big softie for helping out other people. Yeah, that can be a good thing, but often the perpetrators always use this to their advantage. They may disguise themselves as a fellow bicyclist with a flat or an injured runner. Making you feel obligated to stop to help them. I always make sure that when I am on a trail or on the road, I look for possible weapons laying around me such as a stick or rock, even my keys (this is why the pockets on your jersey is great) to stab out their eye, and I always look for quick exits to allow myself the opportunity to get out of the situation, which may require me to abandon my bycycle.