Story highlights Brian Schober was on his way to work when incident occurred

He used trooper's radio to summon help

(CNN) At 4:45 a.m., Interstate 10 west of the tiny town of Tonopah, Arizona, can be a pretty empty, isolated and dark road.

Brian Schober was driving to his job in Yuma on Thursday when he came upon the bright lights of a stopped police SUV and a man waving his hands, asking for help.

When Schober got out of his pickup truck, he saw two men on the pavement, both shot.

One was Ed Andersson, an injured Arizona state trooper. The second was a man authorities said had been beating the trooper after shooting him twice. The man who flagged Schober down had fatally wounded that attacker minutes before Schober stopped to see what was going on.

A woman was on the ground, too, having been ejected from a car that had crashed off the side of the highway. She died from her injuries.

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