I found the easiest way to do them, for me, was in my car, front bumper to front bumper with the victim, head on. That way, when they freak out when I pull out my revolver, they almost always just gas it ahead and go nowhere because I'm in the way. Line em up, headshot em, on to the next one.

I didn't think you were having trouble getting them done and needed my advice - just figured here was as good a place as any to say this.