David Machado killing
David Machado (R) is believed to have murdered and Stanislaus County Sheriff's Deputy Dennis Wallace (L) Stanislaus County Sheriff's Department, California Highway Patrol

A fugitive 'executed' a deputy sheriff in California before being arrested when he tried to snatch a woman's purse, say police. Officials believe that David Machado killed Stanislaus County Sheriff's Deputy Dennis Wallace by shooting twice in the head from point blank range in the early hours of Sunday morning.

A few hours later, 150 miles away, Machado was arrested after trying to steal a purse from a woman, who fought back and called authorities, police say. Wallace was said to have been investigating reports of a suspicious van parked outside the city of Hughson, in central California.

Wallace was said to have been by himself when he came across the van after being told the vehicle was stolen. Wallace asked for backup and another deputy found the dead officer a short time later.

"We believe that Deputy Wallace was killed outside of the car, and we know for a fact that the gun used in this crime was in direct contact with his head when the trigger was pulled twice," Stanislaus County Sheriff Adam Christianson said in a video posted by news station KCRA3. "This was an execution."

Machado, 36, is believed to have fled in the stolen van before then stealing a white Kia sedan in the nearby city of Keyes, police said. Officials say that he then committed an armed robbery in the town of Lindsay, about 150 miles south of where the shooting occurred.

Christianson said he then tried to steal a woman's purse at a convenience store but when she fought back he ran away before being caught by officers a short time later. Machado was wanted on a felony arrest warrant but authorities have not expanded on what the offence was. "He is a known criminal," Christianson said.

Authorities have recovered the van and the Kia sedan as part of the investigation. Wallace, 53, was said to have been a 20-year veteran of the force and is survived by his wife, Mercedes, and adult children. He becomes the fifth law enforcement officer in the state to die in the line of duty in the last five weeks.