Crowds at The Dallas Zoo witnessed a violent attack Sunday where two male lions killed a lioness.

A spokesperson at the zoo told NBC DFW that at about 2 p.m. one male lion lashed out and killed a 5-year-old female lion named Johari in the "Giants of the Savanna" exhibit. Another male joined in once the attack started. The males are named Denari and Kamaia.

No people were injured, but many witnesses were stunned.

“You could see this lion holding the other one down," said witness Michael Henshaw. "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," said Dylan Parker. "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.”

Lynn Kramer, vice president of animal operations and welfare at the Dallas Zoo believes the male "went right for her [Johari's] throat."

“We think he just grabbed her by the throat and it was very quick," said Kramer. "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.”

Zoo goers said the staff jumped in immediately with barriers to shut the scene down.

Zoo officials said this is the first time anything like this has happened. They also said this is the first time they've seen any "alarming" aggressive behavior from the lions. These lions have all lived together since the exhibit opened three years ago.

The male lions completed a demonstration for visitors Sunday at 10 a.m.

Zoo officials told NBC DFW there is no chance that the male lions who attacked will be euthanized. Meanwhile, they were placed in their individual rooms and fed dinner.

They also said the lions didn't attack for food.

On Monday, it's likely the two remaining females will be roaming their exhibit but the males will be kept away.