Tigers maul worker - Why

I just read the online news and came across this article that reads that 3 white tiger have mauled a malaysian worker to death at our local zoo.
Apparently, the man has jumped into the white tigers enclosure. Read that prior to the fateful accident, the man has been behaving strangly, talking to himself, and told one of the zoo-keeper goodbye, they won't be seeing him anymore.
After a while he left the zoo, before returning shortly, and jumped into their enclosure. Tigers naturally attack their prey so there's no need to sedate them, but weird is why would the man jump over to be attacked.
A very weird method to commit sucide, to allow the tigers to maul on yourself. Nevertheless, he was pronouned dead on the spot from head and neck injuries.
I'm interested to learn from of this case......