"Last night Travis and his family suffered an unspeakable tragedy," Uber said in a statement. "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 investigation into the accident is underway, the sheriff's department said. Officials found the couple on shore, where Kalanick's mother had already died and his father had "moderate injuries."
On Mother's Day two weeks ago, Kalanick shared photos of him and his mother from his childhood on Facebook.
"As time goes on, I appreciate my mom, her infinite love and huge [heart] more and more," Kalanick wrote.
Uber did not immediately respond to a request for comment from Fortune.