PINAL COUNTY, Ariz. — A Good Samaritan was killed in a crash on Interstate 10 in Pinal County Sunday morning.

The crash occurred around 6:30 a.m. on Interstate 10 near mile marker 185 north of Casa Grande, Arizona Department of Public Safety officials said.

Officials say the incident started when the ambulance driver may have fallen asleep. The ambulance lost control, traveled up and down the roadway, then rolled and landed on its wheels near his right shoulder.

The driver and female passenger, both American Medical Response employees, were in the ambulance at the time of the accident. Officials said no patients were transported.

Officials said two Good Samaritans, a man and a woman, who were in another vehicle stopped to help those inside the ambulance. While they were trying to help, a vehicle struck an ambulance and two Good Samaritans.

The Good Samaritan died at the scene. The Good Samaritan woman was taken to the hospital where she sustained unspecified injuries. The woman is expected to survive, officials said.

The man in the ambulance suffered minor injuries, and the woman who was a passenger in the ambulance was taken to the hospital in critical condition.

The male driver who collided with the ambulance suffered minor injuries. An investigation is currently underway to determine whether the man was impaired at the time of the accident.

The individuals involved in this incident have not been identified at this time.

The crash closed I-10 at Casablanca Boulevard for seven hours. All lanes have since reopened.

DPS continues to investigate what led to the crash.