As I write this, the police are still investigating the incident at San Francisco zoo where a Siberian tiger called Tatiana killed one man and severely injured two others.
The article suggests that she may have been "provoked". Obvious enough, though I'd go so far as to say that for any stranger to violate the animal's "territory" in any way is natural and understandable provocation. In a zoo that territory is very clearly defined.
No suggestion of common motive, but a completely different story springs to mind from last year. A man jumped into a lion's enclosure at Kiev zoo apparently shouting out "God will save me, if He exists". You can guess what happened next.