Bonnie Kalanick, the mother of Uber CEO Travis Kalanick, has died in a boating accident. Kalanick's father, Donald, was injured and is in serious condition.

The ride-hailing company said Saturday that the accident took place Friday night in Fresno, Calif.

The couple, in their early 70s, have been longtime boaters. In a memo to Uber staff, Liane Hornsey, the chief human resources officer, called the incident an "unthinkable tragedy." She wrote that "everyone in the Uber family knows how incredibly close Travis is to his parents."

"Last night Travis and his family suffered an unspeakable tragedy. His mother passed away in a devastating boating accident near Fresno and his father is in serious condition. Our thoughts and prayers are with Travis and his family in this heartbreaking time," an Uber spokesperson said in a statement attained by The Hollywood Reporter.

About 5 p.m. Friday, officers were called to the scene of the accident and found a man and woman on a shore off the lake, the Fresno County Sheriff's office said in a statement.

The woman died at the scene, and the man suffered moderate injuries, the sheriff's office said. He told officers the boat had sunk.

An autopsy of the woman is planned, the office said.

Uber identified the couple as the Kalanicks. Donald Kalanick is being treated at a hospital and is in stable condition, the company said.

Crew will try to remove the boat from the lake Saturday, the sheriff's office said.

Kalanick grew up in Northridge and attended UCLA. His mother worked in newspaper advertising sales. The Kalanicks were very supportive of their son's business ventures into various tech start-ups, even welcoming him back home to live with them when one such endeavor failed.

He founded in Uber in 2009.