Visitors at the Dallas Zoo were treated to a display of existential horror Sunday when they witnessed a lion attack and kill one of it's own. The male lion turned on his female companion, Johari, gripping her neck in his jaws until the life left her.

Zoo security responded swiftly, clearing visitors from the exhibit in an attempt to shield them from the incident. But it was too late. "At first you think they're playing; then you realize he's killing her... and you’re watching it," said visitor Michael Henshaw. "You just can't believe your eyes."

Dallas Zoo officials still say they are unsure how this happened. According to vice president of animal operations and welfare Lynn Kramer, the animals involved were born in captivity and had lived peacefully together at the zoo for the past three years. "We've had, you know, a few incidents of rough play, but nothing out of the ordinary," the 35-year zoo veteran told WFAA Dallas. "I've worked in five major zoos, and I've never seen a cat kill another cat before."

The killer, whose name has not been released, was not euthanized, but has been removed from the enclosure and will remain separated from its compatriots for the foreseeable future.