Assault on Precinct 13, but with vampires?

Has anybody here ever seen something like this? I was thinking, it could be a decent idea for a movie. There are a lot of things you could do with the idea. Like, show how one or two vamps gradually infiltrates the police station, and gradually vamps out the whole staff (except for our heroic protagonists, of course). Or, maybe they could take over very quickly, and then THE VAMPS WOULD BE THE POLICE for, whatever town the movie was happening in. So, that could lead to a lot of havoc... but, I mostly just like the idea of some people besieged in a poilice station by vamps.

Any thoughts?