There are a few things you should never do on an elevator -- fart, make eye contact, say any word that isn't a floor number -- and I think it goes without saying "having explosive diarrhea" belongs on this list.
I think it's also safe to say violently pooping in a public place is frowned upon regardless of the locale, but it's especially frowned upon when that place is an enclosed box with no conventional means of escape.
It's for that exact reason elevators are the perfect place to pull off pranks that involve a heavy flow of poop shooting out of your butt. This is one of those pranks.
I should mention I'm a little skeptical the people riding along in the elevator weren't actually in on the stunt because I feel like if I were ever diarrhea-ed on, my reaction would be a little more extreme than the ones on display here.
I can only hope I never have to test out that theory in real life.