Updated May 22: Revised to include additional video.

Richardson police are asking for help after a fit of road rage ended in a deadly shooting Thursday morning on Central Expressway.

The shooting was reported about 6:30 a.m. at the intersection of Arapaho Road and the frontage road of southbound Central Expressway.

Witnesses told police they saw two cars driving erratically on Central's southbound frontage road shortly before the shooting.

The drivers stopped at a red light at Arapaho Road, where they "exchanged unpleasantries," police spokesman Kevin Perlich said.

As the light turned green, witnesses heard a single shot and both drivers took off, the victim headed south and the shooter fleeing east on Arapaho.

Police released new video Monday that showed the cars driving alongside each other. The footage "supports a witness account that the victim in this case may have had the opportunity to disengage, but tragically elected not to do so," police said.

Perlich said the victim continued driving south for about a mile before drifting off the service road and hitting a light pole just north of Belt Line Road.

A Good Samaritan saw the car driving unusually slowly on the frontage road and prevented it from entering the expressway, police said.

Robert Klikus, 27, of Irving was found dead at the scene, Richardson police said.

The shooter remains at large.

Police said the suspect vehicle — a white, four-door 2012 Toyota Camry — was last seen headed east on Arapaho.

On Friday, police said they received tips about the shooting and were following up on them. But they were hoping that the shooter would come forward.

"Usually there's an explanation for why someone did what they did," Perlich said. "We'd like to hear from the person actually involved and not speculate about what happened."

Police believe there may be additional witnesses who saw something on Central Expressway or the Bush Turnpike. Anyone with information is asked to call 972-744-4800.