Here in sweden last year at kolmården zoo a pack of wolves killed one of the staff. They found her mauled
Okay so a number of factors which make this completely different to the picture of the Chinese zoo.
1) The zookeeper went into their habitat on foot, WITHOUT a lookout / backup, in the zoo were I worked we had to clean the glass of the crocs etc and even with those guys you were not allowed to enter without a lookout who would keep an eye on the crocs who would naturaly try to sneak up on you, so she probably done it a million times before guess that wasn't her day.
2) she entered at a crucial time I believe they had either offspring or the pack was in an otherwise usual situation were it is unwise to get to close to them.
Wolf are very very shy, I've been right in the middle of a wolf pack in the zoo were I worked, there is very very very little chance they ever attack you, in fact you have a better chance being attacked by a pack of stray dogs than wolfs, they see you as Apax predators and not as a potential meal, years of hunting and decimation of the two legged hunters has left its mark on their genetic fingerprint and all wolfs see humans as fucking dangerous, that doesn't mean that if they are hungry enough and they have the numbers on their side they would not try to take you down in the wild.