The crash happened on Harmony Road, also known as County Road 38, between Shields Street and College Avenue at around 12 p.m.
Investigators say a Pontiac sedan crossed over into the center lane and collided with a truck traveling east.
The truck’s driver was identified as 42-year-old Brian Sauer. He was taken to the hospital with moderate injuries.
The driver of the sedan was killed. Two children were also inside that vehicle; one was killed, the other has serious injuries. Their identities have not been released.
A stretch of the road was closed for hours, but was reopened about four hours later.
Anyone with information about the collision, who has not already given a statement to police, is asked to contact Officer Drew Jurkofsky at 970-416-2224.
People may also contact Crime Stoppers of Larimer County at 970-221-6868 or www.stopcriminals.org. Callers can remain anonymous.