An Uber driver opened fire early Friday morning on a male passenger after a "conflict" on a highway, according to Denver police.
The passenger, who may have been shot multiple times, was taken to a hospital and pronounced dead following the confrontation, which began around 2:45 a.m. MT (4:45 a.m. ET), said Denver police spokesman Sonny Jackson.
The driver was identified as Michael Hancock, 29, and arrested on a charge of first-degree murder, police tweeted.
Hancock was earlier treated at the hospital for unspecified wounds and released into police custody, Jackson said, adding that investigators "can't speculate what went on in the car."
The passenger was not immediately identified.
Police shut down a portion of the southbound lanes of Interstate 25 through the morning rush hour, causing massive gridlock, as they sought to interview other drivers who may have witnessed the shooting.
Jackson said authorities were in contact with Uber. He said it was unclear if the shooting occurred while Hancock was on a job.
A spokesman for the ride-sharing app said in a statement that the company is "deeply troubled" by what happened: "Our thoughts are with the families of those involved, and we will continue working closely with police."
In a 2016 case in Kalamazoo, Michigan, an Uber driver was charged with fatally shooting six people and wounding two others — apparently at random — and blaming the car service's mobile app for turning him into "a puppet." He remains jailed while awaiting trial.