I've found it! Yes, it has happened.
The funniest story in the history of the universe has been told. And the best part? It's non-fiction. (By the way, don't even bother reading the news story linked above. I'm about to relate the whole thing. It's just there so you know that I'm not lying.)
Over the weekend, the Davis family of Bakersfield, California was visiting their former pet in a sanctuary where he now resides. The pet?

An orphaned chimpanzee named "Moe" which they had adopted while on a trip to Africa. Oh yeah, Moe was in the sanctuary because he bit someone. Okay, well, he bit their finger off, So What? At any rate, it was Moe's birthday, and the couple decided to bring Moe a present: A birthday cake.
The problem arose when two other chimps in the facility, "Buddy" and "Ollie", became inflamed with unresolvable cake envy. Buddy and Ollie somehow managed to escape their cages. Ollie knocked over Mrs. Davis and bit off her left thumb.
In an effort to save his wife, Mr. Davis intervened, at which point Buddy sideswiped him and, according to authorities, "much of
HIS FACE was
CHEWED OFF".
Oh, but the hilarity doesn't end there. Buddy then took it upon himself to tear off Mr. Davis' foot.
THEN it was time to say goodbye to the twins downstairs. That's right, Mr. Davis had his
BALLS RIPPED OFF BY A CHIMPANZEE Then the animals' keepers shot the chimps and blah, blah, but that isn't the point.
Personally, I think whenever a captive animal goes insane and mauls people it is never anything less than
AWESOME. What people don't seem to understand is that, like humans in prison, animals in captivity are going to become increasingly pissed, and eventually they realize that they have nothing to lose, and that's when they go crazy.
So, who's fault is it? Well, the Chimps didn't ask to be locked up, so whatever the handlers get, they clearly deserve. As for the visitors who were mauled, they should've known better than to bring food into a room filled with wild animals. I'm glad the monkey got that guy's nuts because now that dumb fuck can't reproduce more fucking dipshit morons like himself.

Besides, look at that guy. I would've ripped his testicles off too if he got too close to me with a fucking birthday cake.
Watch the video from the AP