Chief of Police Greg Workman said Jonathan King submitted the letter on Tuesday. Workman said King was leaving the force "to explore other employment opportunities."
Workman said King has worked for the department for 2 years and 10 months.
No one was reported injured in the crash in which King was beginning an emergency response and merged into an eastbound lane of traffic. He crashed into a car already in the lane and was then hit in the rear by another vehicle.
"Whenever we are in an accident, the Tennessee Highway Patrol investigates," Workman said Friday afternoon." Workman said he has heard the Highway Patrol report was almost complete and King was not charged.
"There were some of the department's policies which were violated as a result of the accident," Workman said.