PHOENIX -- A man is dead after an officer used a Taser to stun him during a fight early Thursday morning, authorities said.

According to the Department of Public Safety, Arkansas resident Mark Morse, 36, was walking against traffic in the carpool lane of Interstate 17 when the officer tried to arrest him.

He fought back, and after the officer used the stun gun, the man had difficulty breathing, DPS said. He was pronounced dead at a nearby hospital.

DPS said the officer believed Morse was under the influence of some substance.

Phoenix police and DPS will both conduct investigations into the matter.

The Maricopa County Medical Examiner's Office has not released the cause of death.