"Help! A van with license plate XXX-123 just shot at a guy in the parking lot here...hold on, what did you say...[muffled sound]...there's a badge on his belt,

"Help! A van with license plate XXX-123 just shot at a guy in the parking lot here...hold on, what did you say...[muffled sound]...there's a badge on his belt, I think he's a cop from (insert adjacent town). I can still see the van, it just parked down the road at..." You get the idea. Call it in from the nearest pay phone and leave. Guaranteed response. I'd only do this if I lived in an area with a bunch of deadbeat cops. In MA our cops do their job without having to be tricked into doing it...the courts on the other hand seem to let everyone off.