This is a link to a clip of a lion tamer being attacked by her lions, you don't see much as every one jumped up except the person with the camera..........apparently the lion tamer walked out of the ring and is in a stable condition in hospital. Video: Watch: Lion attacks tamer during performance - Telegraph
Maybe they just smelled the blood if she had a cycle? Moscow zoo's annual report (don't remember the issue, one with memoirs) tells that carnivores reacted to female keepers differently in such days.