A 20-year-old Polk County man who was arrested Saturday on accusations of fatally shooting his two roommates later confessed to the crimes, court documents show.

Mitchell Julio Morris confessed in an interview with detectives that he shot his roommates, Bailee Ray Southwick and Mackenzie Lyman. Southwick, 18, and Lyman, 21, were a couple. A probable cause affidavit shows no apparent motive for the shootings.

Morris is accused of three counts of aggravated murder, two counts of murder, and two counts of unlawful use of a weapon, court documents show. Southwick and Lyman were found dead Friday evening in a home they were sharing with Morris in Crooked River Ranch, a resort community in unincorporated Jefferson County.

The affidavit says Morris and his roommates hadn't been arguing or fighting before he shot them.

It says that Southwick was sitting on a couch in the home when Morris came out of his bedroom and shot him. Southwick "slumped over," the affidavit says, and "stated something to the effect of, 'what the f--k?' "

Lyman then came out of her bedroom and said something similar before Morris shot her.

The affidavit says Morris then "threw the gun down," put together a bag and left the home in Southwick's Chevrolet pickup truck.

Morris drove to Salem and stayed with another man, who was riding in the pickup with Morris when he was arrested. Morris also confessed to the man, when being arrested Saturday, that he shot his roommates.

Morris' relationship to the other man was unclear, based on court documents. The other man wasn't arrested and is cooperating with authorities, according to a previous Oregonian/OregonLive report.

Morris is being held in the Jefferson County Jail, according to its inmate roster. His next scheduled court appearance is Friday.

-- Jim Ryan

jryan@oregonian.com

503-221-8005; @Jimryan015