The Dallas Zoo says a female lion died Sunday after it was attacked by another lion.
The attack was witnessed by guests at the zoo.
In a tweet, the zoo said workers were "heartbroken" over the attack, and urged others to send good wishes to the staff.
The lions are part of the zoo's Giants of the Savanna exhibit in a section called Predator Rock, featuring five lions and two cheetahs, according to an undated news release from the zoo.
Workers and visitors at the Dallas Zoo are still coming to grips with Sunday's death of a female lion that was suffocated by the jaws of a male lion.
Zoo officials are still trying to determine exactly what happened to Johari... and why.
It's clear that the unexpected and violent death of this beloved big cat has had a sobering impact on the staff at the zoo.
On Monday morning, the zoo's remaining female lion could be seen sunning herself atop a rock at the Giants of the Savannah exhibit.
Dozens of horrified zoo visitors witnessed Johari's death on Sunday afternoon. Some said the ordeal lasted for 10 minutes.
Vice president of zoo operations Lynn Kramer explained what lions do in their natural habitat.
"There are male coalitions in the wild of two to five males, and sometimes they come in and displace a male that's been the head of a pride," he said. "At that time, it's not unusual for them to kill the cubs and then mate with the lionesses, but it extremely rare that they would attack or kill the females."
The animals involved in Sunday's incident were never in the wild; they were born in captivity.
Zoo workers are being interviewed to see if there were any possible warning signs. They will also review policies and procedures to determine if any changes need to be made.
The two male lions in the exhibit are also being monitored.