The incident began when the homeowner and his roommate decided to go out drinking earlier in the evening. They met two women and brought them to their home in the 9700 block of Mallard Drive.
One of the women apparently clogged up the toilet, and the two men got into a fight. The women left, but the fight continued as the homeowner pulled out a gun and shot his roommate in the chest, said a Thurston County Sheriff's Office spokesman.
The roommate then left and called a friend, who took him to the hospital for treatment of non-life-threatening injuries.
Meanwhile, deputies responded to the home after receiving a report of an assault.
They interviewed the homeowner, who said he shot his roommate in self-defense. He was then taken to a local clinic to be treated for sore ribs and facial lacerations.
So far, no one has been arrested and detectives are investigating.