2 Lions kill lioness at a Dallas Zoo over the weekend, shocking the visitors who could only stand by helplessly and watch.

2 lions, male siblings Denari and Kamaia, attacked 5-year-old female Johari, affectionately known as Jo-Jo, one of the three lionesses at the Dallas Zoo.

Dallas Zoo visitors watched in horror as one of the lions delivered a crushing neck bite to the lioness, killing her. 

Visitors interviewed after the incident say that they had initially thought that the big cats were merely being playful with each other, until they saw signs of the lioness struggling. 

One of the lions had Johari by the throat, while another went in for the kill. When the 2 lions left, Johari lay limp, and the horrifying reality of the wild dawned upon shocked Dallas Zoo visitors. 

Resident vet to the Dallas Zoo, Dr. Lynn Kramer, who has worked in zoos for more than three decades, has said that the lions killing the lioness was a rare occurence. 

"They've been together constantly the past three years. There are prides in Africa with multiple males and females. We really don't know what caused this."

Animal experts say that in the wild, lions would only kill family members if they were sick, or behaving strangely. The Dallas Zoo is however, unsure if Johari had been exhibiting such strange behavior. 

The lioness being killed on a Sunday, the exhibit was opened once again on Monday, but wil males and females in separate enclosures. 

The Dallas Zoo also says that the 2 lions will not be euthanized for their behavior, saying that it might have been an isolated incident.