REEDSPORT, Ore. - The man arrested for shooting a snorkeler in the Smith River near here on Tuesday told police he believed he was shooting at a large rodent.

William Roderick, 60, of Reedsport, was taken to the Douglas County jail Wednesday night on charges of second-degree assault, felon in possession of a weapon and unlawful possession of methamphetamine and marijuana.

Roderick told detectives he was house-sitting a home on Tuesday when he saw what he believed to be a nutria swimming in the river about 2 p.m. Roderick went onto the deck of the house and fired at the object with a .22-caliber rifle, police said.

When Roderick realized he had shot a person, he went to the shore and tried to get help for the snorkeler, 44-year-old John Chessman of Marcola. Chessman, who suffered one gunshot to the head, was listed in serious condition at OHSU in Portland on Wednesday.

Police said Roderick later led investigators to the section of river where he dumped the rifle after the incident. Divers on Wednesday recovered a gun from the river that is believed to be the one used in the shooting.