EMMETT -- A 67-year-old Gem County man is facing charges after investigators say he set four police cars on fire last summer outside the Emmett Police Department.

Darrel Charles Rich was indicted on federal arson charges in December. He is also charged with eluding, DUI and weapons charges in state court stemming from the same incident.

MORE: Emmett police cars set on fire

Idaho State Police began investigating the arson after the parked police vehicles were torched at about 1 a.m. July 27.

Firefighters rushed to the police department, but the marked police cars were left charred and blackened by the time the flames were extinguished.

ISP told KTVB the same day they had developed a suspect in the case, but have not released Rich's motive or how they tied him to the fires. County records show Rich is listed as a registered sex offender stemming from a 1998 conviction of lewd conduct with a child under the age of 16.

Emmett Police Chief Steve Kunka said two of the burned vehicles were in full-time patrol use, while the other two were used for the department's reserve and Citizens On Patrol programs.

Some officers rode double in the remaining cars until the department could purchase two new patrol vehicles, Kunka said. All of Emmett Police's 13 officers now have a car of their own assigned to them, he said.

Rich could face up to 20 years in prison on the arson charges.