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A man was in jail Thursday, accused in the shooting deaths of his mother and a brother on a remote eastern Utah ranch.

Carbon County Sheriff Jeff Wood identified the deceased as Susan Peterson, 45, and her son, James Peterson, 23. Both are from Ferron, in adjacent Emery County.

Another of Susan Peterson's sons — Seth Gordon Peterson, 25, also of Ferron — was arrested Wednesday evening in connection with the slayings.

He was being held without bail, booked into jail on suspicion of two counts of first-degree felony aggravated murder, first-degree felony attempted murder, automobile theft, fleeing police and failure to stop at the command of a police officer.

Formal charges were being screened by the Carbon County Attorney's Office.

Wood said no motive for the slayings had been established.

About 6 p.m. Wednesday, deputies had rushed to the scene, a field outside a farm about 7 miles west of Price and just off State Route 122, on a 911 call reporting shots fired.

Wood added that there were witnesses to the episode.

Seth Peterson was spotted in what later proved to be a stolen car, attempting to drive away from the scene, Wood said.

Seth Peterson was taken into custody after a brief, high-speed chase and foot pursuit. Seth Peterson was not armed at the time of his arrest, but deputies did recover several high-powered hunting rifles at the homicide scene.

Wood said a report of otherwise undisclosed "non-violent, suspicious" circumstances had prompted an earlier visit the same day, about 3 p.m., but it was determined at that time there was no threat, so deputies left.

The victims' bodies were found near a 4-wheel ATV, parked in a field roughly midway between the former mining community of Hiawatha and SR122's junction with SR10.

A search of Utah court records shows no prior criminal cases against Seth Peterson.

A statement from the family's spokesman described Susan Peterson as a "loving mother of 15 children, ages 28 to 3." She was "very active" in her community and church, living her life in a "service-oriented" way and taking care of others.

"She was a very intelligent person, always thirsting for knowledge in bettering herself and her family. Her family was her whole life and she supported them in all they did," the statement says. "Susan always thought of others before herself. Her husband states that she would often go without new clothing and other necessities in order to make sure her children had what they needed. She never wanted for herself.

"James was kind-hearted and would give you the shirt off his back," it continues. "He was very personable, kind, respectful and thoughtful of others."

A GoFundMe page has been set up to raise money for the family, which requested privacy as they mourn, the statement says.

— Tribune reporter Mariah Noble contributed to this story.

Twitter: @remims