Details that came out in paper today sure make me feel like there was human involvement. These details include:
1) presence of sticks and other foreign items in the moat - seems likely the tiger was being provoked.
2) foot prints on the fences and the top of the wall
3) the tiger followed the boys and cornered them - she must have really been angry.
4) the tiger didn;t like the moat and didn't spend time there by herself.
My thoughts: the boys (three teenagers...) were probably provoking the tiger, and accidentally helped her escape. The zoo director thought that perhaps they had been sitting on the wall, throwing things at her, and she used their legs as leverage to get out of the moat. She had attacked her keeper last year, so was probably somewhat easily provoked as it was. She escaped, killed one boy, and followed the others.
Statements n the NY Times suggest that the zookeeper somewhat blames the police force for deadly fire - they say that they had tranquilizer guns ready, but the police wouldn't use them. I can't say I blame them - with one already dead and the tiger standing over the other two, having mauled them, and with no idea how many other people were dead, it seems like opening fire was sadly inevitable.
It also sounds like there was an absolute lack of communication within the zoo. If the boys were taunting the tiger, even that close to closing time, was there really around to stop them? Why no security cameras? Why no better way to interface with the police - disaster preparedness?