Officers were called just before noon Saturday to the collision on Point Reyes-Petaluma Road just west of Hicks Valley Road.
The initial caller said that four cyclists were involved in a collision but later officers learned a vehicle was also involved and its driver drove away from the scene.
Witnesses told officers that a dark blue Dodge Ram pickup truck was traveling west on Point Reyes-Petaluma Road when the driver appeared to swerve to the right and intentionally drive into the group of cyclists.
All of the cyclists were injured and one was flown to a hospital because of the extent of his injuries.
CHP-Marin released images of the suspect on their Facebook page.
Bay City News contributed to this report.