A motorist was killed and an Illinois State Police officer was seriously wounded in a shootout early Tuesday on Interstate 64 in downstate Mt. Vernon.

The trooper had pulled off to the side of the interstate around 3 a.m. to help a woman and a man stranded in their vehicle, according to the state police.

After a second trooper arrived, an “altercation” took place between the driver of the vehicle and a shootout ensued, state police said.

Brandon Griffin, 23, of Albuquerque, N.M. was pronounced dead at the scene, officials said.

A trooper was shot and taken in serious condition to a hospital. His injuries were not thought to be life-threatening. He has been with the state police for 16 years,

State police did not say what led to the altercation but said the agency’s internal investigators were handling the case,

The shooting happened near Mt. Vernon, about 80 miles southeast of St. Louis.