Dallas Zoo Lion Attacks and Kills Lioness in Front of Visitor Groups, Staff Still Unsure What Prompted Assault (VIDEO)

Visitors of The Dallas Zoo witnessed a violent brawl between two lions in which one of the animals was killed this past weekend.

The assault occurred at about 2:00 p.m. at the "Giants of the Savanna" exhibit on Sunday.

No people were injured after a male lion attacked female lioness Johari, who lived in the same enclosure, but many described the event to NBC's local station in Texas as downright shocking.

"At first you think they're playing, and then you realize he's killing her, and...you're watching it and you just can't believe your eyes," witness Michael Henshaw told NBC. "You could see this lion holding the other one down. There was no blood, but it held her down for about 10 to 15 minutes 'til she was lifeless."

"We were right there at the front of the glass," another eyewitness, Dylan Parker, told WFAA. "It was just traumatic. You could see the larger male lion kind of attacking the smaller lioness, and they were just going at it nonstop."

Vice President of Animal Operations and Welfare at the Zoo Lynn Kramer said that the male simply "went right for [Johari's] throat."

"We think he just grabbed her by the throat and it was very quick," Kramer told NBC. "I've been in the zoo business for over 35 years. I've worked at five major zoos, and I've never seen a cat kill another cat before."

Bystanders reported the staff leapt into action once they realized an assault was underway. Zoo employees were just as stunned as the witnesses, and told reporters that they'd never seen anything like it. This was also the only instance in the recent past where the lions exhibited such "alarming" and aggressive behavior. The animals have lived in the zoo together since the exhibit began in 2009.

Zoo officials said they were still unsure why the lion attacked the lioness in the first place. The animals were well-fed and relatively calm earlier in the day.

Employees also told NBC that the lions would not be put down for the attacks, but on Monday, staff would most likely separate the two females in the exhibit from the other males.