Remote target shooting
That Platt and Matix posed as ordinary target shooters in order to ambush and kill other target shooters for their guns and cars----this is not the first or last time it has happened. There was an incident, also in Florida along similar lines and there have been several cases of hunters targeted and killed by either madmen fugitives or eco-terrorists.
It's difficult to be so wary all the time. Some guy stops, he seems friendly, asks if he may take a few shots from his piece, offers to let you try his gun, then asks, or you offer to let him try yours, you turn your back for whatever reason and it's all over. As a few have said, perhaps it's best not to be alone at a remote shooting pit.
Int'l Assoc. of Law Enforcement Firearms Instructors