From the BBC,
US zoo baffled by tiger’s escape
Investigators are trying to establish how a tiger escaped from its grotto at San Francisco Zoo and attacked three visitors, killing one.

It’s not an investigative response that breeds immediate confidence, but you can imagine the uproar if the opposite was true. “Oh, it was obvious! The tiger crawled through the man sized hole in the wall left unrepaired the last month!” No shit they’re baffled.