Panda

A panda walks into a café. He orders a sandwich, eats it, then draws a gun and proceeds to fire it at the other patrons.

"Why?" asks the confused, surviving waiter amidst the carnage, as the panda makes towards the exit.

The panda produces a badly punctuated wildlife manual and tosses it over his shoulder. "Well, I'm a panda," he says. "Look it up."

The waiter turns to the relevant entry in the manual and, sure enough, finds an explanation.

"Panda. Large black-and-white bear-like mammal, native to China. Eats, shoots and leaves."