A female lion unexpectedly attacked the father of her three cubs at the Indianapolis Zoo — and killed him.

“An unusual amount of roaring from the outdoor lion yard” was heard by animal care staff early morning on Oct. 15, according to a statement released Friday by the Indianapolis Zoo.

Employees saw an adult lioness named Zuri being hostile with 10-year-old Nyack, a lion on loan from the San Diego Zoo.

“She had Nyack by the neck. Keepers came up and saw what was occurring and made an attempt to separate the two. But she continued to hang onto Nyack by the neck until he stopped moving,” David Hagan, curator of the Indianapolis Zoo, told Reuters.

Our Zoo family is sad to announce 10-yr-old male lion Nyack has died. Earlier this week he was injured in a physical incident with female lion Zuri. We will conduct a thorough review to attempt to understand what may have led to this. pic.twitter.com/hQD2hOAaCp — Indianapolis Zoo (@IndianapolisZoo) October 19, 2018

Sukari, the 3-year-old daughter of Zuri and Nyack, was in the lion yard at the time of the attack.

An animal autopsy, known as a necropsy, was conducted by the zoo’s veterinary staff and confirmed Nyack died of suffocation from neck injuries.

“They were compatible with no outward indication that an event like this would occur,” zoo officials said in the press release.

Both Nyack and Zuri were part of a Species Survival Plan and had lived together for eight years.

14 PHOTOS Inside the Indianapolis Zoo See Gallery Inside the Indianapolis Zoo INDIANAPOLIS, IN - SEPTEMBER 29: Rhinoceros, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Flamingo's, flock at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Crested Couz, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: A mother and baby Elephant, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Superb Starling, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) In this Friday, May 6, 2016, photo, the main entrance to the Indianapolis Zoo is shown in Indianapolis. The zoo uses dynamic pricing, with ticket prices changing daily, costing anywhere from $8 to $30. Saturdays and Sundays tend to be the most expensive. (AP Photo/Michael Conroy) INDIANAPOLIS, IN - SEPTEMBER 29: Helmeted Guinea Foul, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: White-Cheeked Turaco, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Crested Couz, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Female African Lion, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) In this Friday, May 6, 2016, photo, visitors to the Indianapolis Zoo line up to purchase tickets at the box office in Indianapolis. The zoo uses dynamic pricing, with ticket prices changing daily, costing anywhere from $8 to $30. Saturdays and Sundays tend to be the most expensive. (AP Photo/Michael Conroy) INDIANAPOLIS, IN - SEPTEMBER 29: Cheetah, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Elephant, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) INDIANAPOLIS, IN - SEPTEMBER 29: Bald Eagle, at the Indianapolis Zoo, in Indianapolis, Indiana on SEPTEMBER 29, 2012. (Photo By Raymond Boyd/Michael Ochs Archives/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

Animal care staff had never reported abnormal aggression, injuries or wounds between Nyack and Zuri before the unexpected attack.

“Nyack was a magnificent lion & will be greatly missed. We appreciate the support from our community as we cope with the loss,” the zoo tweeted.

A “thorough review” will be conducted by the Indianapolis Zoo in attempt to understand what caused Zuri to attack her longtime partner.

Following Nyack’s death, the zoo does not plan on changing how it manages lions, and Zuri will remain in her female pair group with her daughter Sukari.

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