A domestic dispute erupted into a double slaying after a possible good Samaritan stopped by a crashed SUV in a Phoenix suburb, police said Wednesday.

Police in Mesa, Arizona, said in a court document that 38-year-old Christopher Glen Wright told them he shot a man who pulled up in a pickup early Tuesday morning next to where Wright had intentionally crashed.

Police later identified the man who was killed as 49-year-old Tomas Olivas Ornelas.

According to the court documents, Ornelas' pickup had stopped at a roundabout at a freeway interchange where Wright had crashed in an attempt to kill his wife, 41-year-old Nasbah Laverne Wright.

Detective Nikolas Rasheta, a Mesa police spokesman, said it's not certain why Ornelas stopped, but he may have been a good Samaritan trying to help.

"Unfortunately we probably will never know why he stopped," Rasheta said during an interview Wednesday.

From what Christopher Wright told police and what was found at the scene, it appears Wright's wife got out of the crashed SUV and ran up to Ornelas' pickup to get help before the shooting started, Rasheta said.

Rasheta said Ornelas was heading to work at a nearby construction site when he was killed. He had no connection to either of the Wrights, the police spokesman said.

Both Ornelas and Nasbah Wright's bodies were found lying on the pavement on opposite sides of the pickup. Police said in the court document they found a rifle on a seat in the SUV. Twenty expended shell casings were on the ground next to the SUV, police said.

Christopher Wright surrendered to police at the scene.

He remained jailed Wednesday on suspicion of first-degree murder and other crimes. He didn't have an attorney who could comment on the allegations when he made an initial court appearance.