I would not worry about it...
... at a haunted house, party, etc. There, one expects such things.
What I do wonder about is the trend toward "reality" shows where people pull stupid pranks on unsuspecting friends. For instance, the scary guy with an axe, machete, or chainsaw pops out from a corner and acts as though he will attack.
I'm pretty sure none of my friends would be dumb enough to set up a stunt like that, but I wonder what precautions such shows take to ensure that the "victim" won't pull a weapon and shoot the simulated attacker.
I've had that thought since the first time I stumbled across one of those shows, a few years back. It was reinforced last week when we went to see "Zombieland."
Great movie, by the way. You'll understand what I'm talking about immediately, if you've seen it.
Cheers,
M