A 19-year-old man — who allegedly suffers from mental illness — remains in the Davis County Jail as detectives complete the investigation of his father's shooting death over the weekend in the boggy Farmington Bay.

James Gully, 61, Holladay, was shot once in the head at point-blank range with a shotgun about 7:15 p.m. Saturday. Gully was duck hunting with his son, Ben Gully, Davis County Sheriff's Lt. Brad Wilcox said.

The gun with which Ben allegedly fired at his father was a hunting weapon. Wilcox did not know if the father also was armed at the time of the shooting, Wilcox said. He did not know what precipitated the shooting.

A statement faxed Sunday to the Deseret Morning News from James Gully's wife, Janice, said Ben had been struggling for about a year with "severe mental illness."

"All of us know that it was not Ben who harmed his father, but the illness itself," the statement said.

No one witnessed the shooting. The Gullys were by themselves in an area where canals, dikes and berms cut through dense brush near the edges of the Great Salt Lake. Hunters in the area stand among thick, tall reeds that limit visibility. "You can only see straight up," Wilcox said.

"You can be 15 or 20 feet away from someone out there and not have a clue they are there. When you're out hunting, you try to keep your voices down because you'll scare the birds away," Wilcox said.

The two or three people also hunting ducks were nearby, about a mile west of the western end of 1600 North in West Bountiful. They heard commotion after the gunfire, Wilcox said, adding that Ben Gully was "ranting" or "rambling".

The other hunters were drawn toward him. They found an armed Ben, and James Gully's body nearby, Wilcox said.

The hunters got Ben Gully to drop the gun, and Ben Gully talked. "He made some statements to the witnesses that I really can't get into. He gave the witnesses the impression that he had done this," Wilcox said.

The deputies who first were called to the scene spent 30 minutes getting there. The deputies had to rendezvous with some people who had a boat and were then transported along a canal. They finally walked from the water to the scene, Wilcox said.

Deputies confirmed the shooting death and pinpointed their exact location along the expansive Farmington Bay. The detectives got to the scene by roads in the area, Wilcox said.

Detectives photographed, diagrammed and collected evidence until about 1:30 a.m. Sunday, when James Gully's body was transported to the Utah State Medical Examiner's Office. The autopsy was performed Sunday, but Wilcox did not know the results.

Detectives returned in the daylight of Sunday "to make sure we had nothing missed," Wilcox said.

Ben and James Gully were close, according to the statement of James' widow. The family always feared that Ben would harm himself, but they did not think he was capable of harming others, it said.

James Gully was devoted to his son and wanted to help him "navigate the bewildering morass of mental illness," the statement said, adding that the family asks for privacy and prayers.

The Davis County Sheriff's Office had no record of a criminal history for either Ben or James Gully, although Wilcox noted the father and son lived in Salt Lake County. Wilcox could not comment on Ben Gully's mental state. He said it will be sorted out if prosecutors prepare a case.

In the meantime, Ben Gully remained in jail Sunday for investigation of criminal homicide, Wilcox said.

E-mail: lhancock@desnews.com