(CNN) A lioness killed the father of her three cubs at the Indianapolis Zoo this week.
In a statement Friday, Indianapolis zoo staff said they heard "an unusual amount of roaring" at the lions' outdoor yard early Monday morning.
When they arrived, they saw a female lion, Zuri, in a physical confrontation with their adult male lion, Nyack.
"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.
Zoo veterinary staff conducted a necropsy on Nyack and found that the 10-year-old male died of suffocation from injuries to the neck.
The two lions were housed together at the Indianapolis Zoo for eight years and produced three cubs, zoo officials said. According to staff logs, there were no previous examples of aggression between Zuri and Nyack.
"We know many people loved visiting Nyack. He was a magnificent male lion and left his legacy in his three cubs," the zoo said in a statement.
The Indianapolis Zoo said it will investigate the incident and there are no current plans to change how they manage the lions. The attack occurred before the zoo opened to the public Monday morning.