The mother of the CEO of the ride-hailing company Uber died in a boat accident Friday evening in Fresno County, the company said.

Bonnie Kalanick, 71, died after the boat she and her husband, Donald, 78, were riding hit a rock in Pine Flat Lake in the eastern part of the county, authorities said.

They are the parents of 40-year-old Travis Kalanick who founded Uber in 2009. The company has since grown to become an international operation with a market value of nearly $70 billion.

The couple from the Los Angeles neighborhood of Northridge 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.”

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

Bonnie Kalanick died at the scene, and her husband suffered moderate injuries, the sheriff’s office said. He told officers the boat had sunk. Both have been boating in the area for the past 30 years.

An autopsy of Bonnie Kalanick is planned, the office said.

Donald Kalanick is being treated at a hospital and is in stable condition, the company said.

Crews will try to remove the boat from the lake Saturday, the sheriff’s office said.