Stark County serial killer Thomas Lee Dillon died last week while being treated in a state hospital.Dillon, 61, died Friday at the Ohio State University Medical Center in Columbus. He died of apparently natural causes after about three weeks in the hospital, a state prison spokeswoman said.Dillon, a former Pike Township resident and Canton Water Department draftsman, tracked and killed five outdoorsmen between 1989 and 1992. He was sentenced to life in prison with parole possible after 165 years after pleading guilty to the murders to avoid a death sentence.The shootings took place in Tuscarawas, Belmont, Muskingum, Coshocton and Noble counties.Dillon was serving his sentence at the Southern Ohio Correctional Facility near Lucasville. He was moved to the hospital Oct. 4.Prison officials did not release the nature of his illness.His wife, Catherine, still lives in Stark County. She could not be reached for comment Thursday.