One of the lions at the Dallas zoo suddenly turned on a lioness in the same enclosure Sunday, killing her in front of the zoo’s horrified visitors.

Witnesses spotted the male lion at about 2 p.m. local time when it appeared he was playing with one of the exhibit’s female lions, five-year-old Johari. He had her by the neck and was apparently roughhousing with her, but the horrified witnesses soon realized that that was not the case.

"The male lion that started it just had his mouth over her throat, and everyone thought they were playing at first," witness Jim Harvey told WFAA 8. "But then they could see she was struggling."

Another witness who was at the exhibit, Michael Henshaw, spoke of the shock that everyone in the crowd felt at seeing the two lions.

"At first you think they're playing; then you realize he's killing her... and you’re watching it," said Michael Henshaw. "You just can't believe your eyes."

The male lion had a firm hold of Johari’s neck for anywhere from 10 to 15 minutes before her body eventually went limp, reports NBCDFW. Witnesses said that there was no blood.

BBC reports that the autopsy of the lioness revealed that she died from injuries to her neck as well as hemorrhaging.

The zoo’s workers are shocked and are trying to figure out just why the male lion attacked Johari.

The lion exhibit opened three years ago with three females and two males, and the lions have lived peacefully together since the first day that they were put on display. Zoo officials said that they have never seen aggression from the lions akin to what occurred on Sunday.

There are no plans to euthanize the male lion, but all the males and females in the zoo have since been separated.

No people were injured in the attack, as the lions were behind the exhibit glass when the incident occurred.

Image: Wikimedia Commons