Deputies said 23-year-old Bryan B. Wrigley, from South Carolina, was riding his bike westbound on County Road 214 when a passing vehicle hit him.
Witnesses told investigators they saw a dark blue extended cab Ford Ranger pickup truck, similar to the one in this picture.
They indicated that the man driving the truck was in his 20s and that they last saw him headed south on State Road 13 towards State Road 207.
That truck should have damage to its front driver's side bumper and headlight area, investigators said, and it could be leaking fluids.
Anyone with information on the driver or the truck should contact the St. Johns County Sheriff's Office at 904-824-8304.