A female African lion killed her long-time mate and the father of her three cubs earlier this week at the Indianapolis Zoo, officials said.

Zookeepers heard an “unusual amount of roaring” and rushed to the lion area to see Zuri fighting with 10-year-old Nyack near the lions’ daughter, Sukari, according to officials.

Zookeepers tried in vain to break up the adults, but Zuri clamped her jaws on Nyack’s neck.

“Zoo personnel made every effort to separate the lions, but Zuri held Nyack by the neck until he stopped moving,” the zoo said in a statement.

Nyack died of suffocation from his neck injuries.

Zuri gave birth to three cubs fathered by Nyack in 2015. They lived together for eight years, according to officials. There was no previous aggression between the animals.

Zuri and the cubs — Sukari and the males Mushaka and Enzi — were not injured in the fight.

“Detailed daily logs maintained by the animal care staff did not report any unusual aggression, injuries or wounds between Zuri and Nyack prior to Monday’s incident,” the zoo’s statement said.

“We don’t know what the precursor to the fight was,” zoo curator David Hagen told WIBC-TV. “They had been together for eight years and during that time that had done really well together.”

“The staff is devastated by the loss,” he added. “He was a friendly, playful lion.”

The zoo is launching an investigation.

A zoo Facebook post said that Nyack “was a magnificent lion and he will be greatly missed.”

He was described on the zoo’s web page as “very vocal and laid back,” while Zuri was described as a “protective mother.”

There was an outpouring of grief and support for zookeepers over the death of the big cat, clearly a favorite of zoo visitors. Several Facebook comments were posted by people who cared for Nyack as a cub in San Diego. He was on loan to the Indianapolis zoo from California.