'One Tree Hill' actress Sophia Bush is left heartbroken after her former boyfriend Dan Fredinburg, a Google executive, was tragically killed in a Mount Everest avalanche caused by an earthquake in Nepal.

Fredinburg's sister Megan confirmed the news on Instagram on Saturday.

"I regret to inform all who loved him that during the avalanche of Everest early this morning, our Dan suffered from a major head injury and didn't make it," she wrote.

Bush and Fredinburg started dating each other in March 2013 before calling it quits in February 2014. In an emotional Instagram post, Bush remembered Fredinburg as "one-of-a-kind", reports eonline.com.

"There are no adequate words. Today I find myself attempting to pick up the pieces of my heart that have broken into such tiny shards, I'll likely never find them all," she wrote.

"Dan Fredinburg was one-of-a-kind... He was one of my favorite human beings on Earth. #goodbyesweetfriend #savetheice #Nepal," she added. Fredinburg is among the 18 climbers who have lost their lives in the 7.9-magnitude quake that had its epicentre in Lamjung district, around 75 km northwest of Kathmandu.