It happened Wednesday around 5 p.m. on the 210 Freeway in San Bernardino, west of Del Rosa Avenue.
The California Highway Patrol said the California Department Forestry and Fire Protection truck heading east on the 210 when it rear-ended a Ford Focus.
The driver of the Focus, identified as 48-year-old Gregory Kirwin, was pronounced dead at the scene.
Kirwin's car rear-ended another a Chevy Impala. The drivers of the Impala and the truck both suffered minor injuries.
The cause of the crash was under investigation.