According to court documents, John Derosia told detectives he beat a co-worker unconscious before setting fire to his condominium in the Alpental area in July of 1978.
Derosia was spotted in the area of the fire and even knocked on doors to warn residents, but he denied any involvement in the crime, according to court documents.
Detectives suspected he started the fire, but they couldn't find enough evidence to charge him at the time.
The 59-year-old was later convicted of an unrelated murder in Snohomish County. He was out on work release Tuesday when he decided to turn himself in.
He waved his first court appearance on Wednesday and is being held on $100,000 bail.