Free-Photos/Pixabay A lioness has killed the father of her three cubs, suffocating her mate by inflicting injuries to his neck at the Indianapolis Zoo. Zookeepers had never before noticed any aggression between the two lions, the zoo said in a statement issued on Friday. Staff members at the zoo said they're "not sure what provoked" the attack. The lions had been held together at the zoo for eight years and produced three cubs in 2015. (Reuters) — A lioness has killed the father of her three cubs, suffocating her mate by inflicting injuries to his neck at the Indianapolis Zoo in an attack not fully understood by zoo staff. The lions had been held together at the zoo for eight years, producing three cubs in 2015, and zookeepers had never before noticed any aggression between the two, the zoo said in a statement issued on Friday.See the rest of the story at Business InsiderNOW WATCH: 7 outdoor adventures that are worth the hikeSee Also:A bride-to-be called off her dream wedding a week before it was supposed to happen — and then donated it to a couple she's never metMeghan Markle wore a young fan's handmade pasta necklace with her $873 dress10 tips for picking out the perfect engagement ring