Wladimir Klitschko mourns former fiancée Hayden Panettiere, vows to keep her memory alive for daughter Kaya

Wladimir Klitschko is mourning his former fiancée Hayden Panettiere , saying the actress remained an "important part" of his life and promising to keep her memory alive for their daughter, Kaya.

"Our family is going through a time of profound shock and grief," the Ukrainian former heavyweight boxing champion wrote on Instagram after Panettiere’s death at 36 .

"She left this world far too soon." Klitschko, 50, said that although Panettiere was "no longer my partner," nothing could erase the time they shared or her place in their lives.

HAYDEN PANETTIERE: A LIFE IN PICTURES "To our daughter Kaya, I will always speak of her mother with respect and make sure she remembers the person she was," he wrote.

The words echoed what Panettiere told Fox News Digital in July about a promise she and Klitschko had made: never to speak badly about each other to their daughter.

"Wlad and I have a good relationship," she said.

"We made a promise to each other that we would never say a bad word about each other to our child.

That was something that I grew up with.

And we’ve stuck to that." Panettiere died Sunday in South Carolina .

The Greenville County Coroner’s Office and Greenville City Police Department are investigating her death.

A preliminary autopsy found no signs of trauma that contributed to her death.

Her cause and manner of death remain pending.

Panettiere transferred custody of Kaya to Klitschko in 2018, saying she knew she was in a bad place at the time and wanted to protect her daughter.

"I just knew that if I wanted to ...