Police found the victim, a 24-year-old man, at a home at 45 Marquard Ave. with a gunshot wound to the stomach at about 12:40 a.m., San Rafael police spokeswoman Margo Rohrbacher said.
The victim told police he had been shot by his 49-year-old roommate, Edward "Fitz" Outcalt, Rohrbacher said.
San Rafael police set up a perimeter and searched the neighborhood for Outcalt with the help of San Anselmo, Fairfax, Twin Cities and Novato police and the Marin County Sheriff's Office.
Within an hour they found Outcalt hiding in some bushes at West Street and Marquard Avenue, Rohrbacher said.
Outcalt was arrested at about 2 a.m. and booked into Marin County Jail for assault with a deadly weapon causing great bodily injury. He is scheduled to be arraigned in Marin County Superior Court on Tuesday afternoon.
Police found a gun believed to have been used in the shooting, Rohrbacher said.
The victim was taken to Marin General Hospital where he underwent surgery.