A driver with Laclede Cab in St. Louis County and the passenger got into a scuffle around 4 a.m., prompting the driver to stop on Interstate 55, KMOV-TV reported.
During the incident, the driver pulled out a gun and shot the passenger, who died from their injuries, Missouri State Highway Patrol Cpl. Justin Wheetley told Fox News. The driver also sustained a gunshot wound, he said.
"There was obviously a struggle going on when he pulled a weapon," Wheetley said.
The driver was taken to a hospital where they underwent surgery and is listed in stable condition. Authorities have not disclosed the identity of the passenger and no arrest has been made.
Investigators have not talked with the taxi cab driver as of Wednesday afternoon and it was unclear what started the deadly altercation, Wheetley said.
Fox News has reached out to the cab company.
The interstate was closed for about four hours while troopers were at the scene.
A Laclede Cab driver was shot and killed in 2018 when a passenger carjacked him and left his body on the street.