A Granite Falls man was killed early Saturday on Interstate 5 in Marysville when his car was rear-ended, law-enforcement officials said.

The 22-year-old man was either stopped or driving very slowly on I-5 shortly after 3 a.m. and was struck from behind by a truck, according to the Washington State Patrol. The car struck a guardrail and the truck rolled and slid on its roof before also striking a guardrail.

The driver of the car died at the scene. The second driver was injured and taken to a hospital.

It’s unclear why the first car had stopped or was driving slowly on the highway, State Patrol spokeswoman Trooper Heather Axtman said Saturday afternoon.