TONOPAH, Ariz. – A suspect is dead and an Arizona Department of Public Safety trooper is recovering after he was ambushed and shot early Thursday on Interstate 10, according to DPS officials.

DPS director Col. Frank Milstead said the suspect was shot and killed near Tonopah by a good Samaritan who pulled off the interstate to help the trooper.

Authorities say a possible motive for the attack on the trooper remains unclear.

The shooting occurred at the scene of a rollover crash in which a woman was ejected and fatally injured.

DPS officials say Anderson spotted the wreck as he responded to a report of shots being fired at another motorist’s vehicle.

Milstead said a call came in early Thursday morning from a driver who said their car had been shot at from the median of I-10 at milepost 81 — just east of California.

The trooper was on his way to investigate the call when he discovered a rollover crash near milepost 89.

A woman had been ejected in that crash — she was later pronounced dead.

Milstead said as the trooper began blocking off lanes of traffic and laying out flares, he was ambushed by the suspect.

The suspect shot the trooper in the right shoulder, and was “getting the better of the trooper” in a fight that immediately followed.

Milstead said the suspect was on top of the trooper striking his head on the pavement.

According to Milstead, a man traveling westbound on I-10 with his wife in the car, pulled over to help the trooper.

The man retrieved a gun from his car and fired at the suspect after the suspect refused to stop attacking the trooper, Milstead said.