SIOUX FALLS, S.D. -

An 18-year-old Sioux Falls man is in critical condition after police say he was attacked by his roommate Friday night.

Police say 50-year-old Todd Thies was arguing with the male victim at their home on the 2200 block of East 8th Street. They say Thies repeatedly punched the teen and he fell down a flight of stairs. Police say the victim hit his head and was knocked unconscious from the fall. They say Thies fell on top of the victim and began strangling him.

According to police, the victim suffered multiple injuries including a fractured skull and a brain bleed. Police say that both men had been drinking.

Thies is charged with aggravated assault.