Thanks, it was also my impression that Zimmerman was part of a group, not a self-appointed vigilante.
Self appointed in the sense that he piped up at a meeting, or otherwise suggested to the neighborhood association that a neighborhood watch would be a good idea, in light of the recent burglaries and hot breakins. As is not unusual when somebody suggests a task, they are also assigned it. I don't know how many others, if any, schedule time to watch the neighborhood. We do know he's not the only one calling the police. He makes about 10% of the calls from the community.