Arson
(http://www.gambling911.com/files/imagecache/slide_image/publisher/arson-033111L.jpg)
My idea is quite simple and not over complicated at all. Basically, the idea is arson; obviously. Now, I'm not talking something predictable like a UCH burning or faggots throwing Molotov's at P1 shops or the Nexus as that is just dumb. But this would actually take place in Precinct 3. What happens is an event character or whatever goes and lights a fire that quickly begins to rage in that precinct and for whatever reason burning debris falls into the P3 tunnel (The kinks can be straightened out later, I'm just trying to get my point across) that blocks both entrance and exit from P3. That way citizens can't get out and units can't get in. After a while the fire begins to grow worse and worse and citizens that are trapped in the precinct can either:
A. Cooperate to survive.
B. Be a selfish jerk and screw everyone over to save themselves...
C. Die.
D. Wait for help?
E. Alternative custom choice that I can't think of.
This would be good because it gives an actual citizen based event and not something that the citizens get locked up in the UCH while the CCA have their fun. Obviously this would have to be done when there are a substantial amount of citizens in P3 and on the server in general. But then that's not even the end of it. This event can then go so far as to even include CCA and even CWU. Medial treatment obviously as the citizens that do manage to escape would surely be suffering from first to third degree burns and can be dealt with accordingly. I'd even be willing to make a character specifically for this event to just die to add some flare to it. Burn alive, crushed by debris, killed by other citizens in panic, etc.