A San Jose man died Saturday evening when his 2009 Lexus careened off I-280 in Los Altos Hills and struck trees before overturning, the California Highway Patrol reported.

The driver, 50, was not wearing a seatbelt and suffered fatal injuries, CHP Officer Art Montiel said. The Santa Clara County Coroner’s office did not release the victim’s name Sunday pending notification of next of kin.

Montiel said the driver reportedly was traveling 100 miles per hour at 5:39 p.m. before going up a drain embankment and then down a ravine.

“At this point, we don’t know for what reasons,” Montiel said.

No other cars were involved in the accident that left the No. 4 southbound lane of I-280 closed until about 10:45 p.m., Montiel said.