About a guy who's going to shoot up his workplace?

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I'm remembering this scenario (from a movie I think, but it might have been from some weird TV show)...

An office employee decides he's going to shoot up his workplace and kill all his co-workers. He brings a gun to work, puts it in his desk and plans the exact time he's going to go on his killing spree.

In a twist of extreme irony, just before the clock strikes the hour of his planned attack, one of his co-workers pulls out a gun with the idea that HE is going to go berserk and shoot up the office!

This leads the guy who was originally going to be the madman to pulling his gun out and either shooting or somehow stopping his equally insane co-worker from carrying out an attack.

This action now makes the initial madman a hero in the eyes of his co-workers and employers with no one the wiser that he was planning to mass murder them all, and (not sure if I remember this correctly...) somehow changing the course of his life which, if his plan had seen fruition, would have most likely led to his own demise.

Any clues?



Yep! That was it.
I was even thinking of Christian Slater but... A.) I couldn't remember his name and.. B.) I wasn't sure it was him!

Now I can't remember if I actually saw this movie (in its entirety) or only caught part of it because I still can't remember anything after the shooting scenario.



Yep! That was it.
I was even thinking of Christian Slater but... A.) I couldn't remember his name and.. B.) I wasn't sure it was him!

Now I can't remember if I actually saw this movie (in its entirety) or only caught part of it because I still can't remember anything after the shooting scenario.
Is this a (dark) comedy or a drama? Sounds like it could be a really good version of either