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DALLAS (CBSDFW.COM) – Authorities are searching for a gunman who, witnesses said, used a rifle to attack three people. The incident started at a restaurant in Richardson and may have continued down a busy North Texas highway, finally coming to an end along the southbound Central Expressway service road, just past Fitzhugh Avenue, in front of the CBS Radio building.

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It was around 3:40 a.m. early Thursday morning when there were reports of shots fired outside of an IHOP restaurant near the intersection of Central Expressway and Spring Valley Road in Richardson. People inside of the restaurant saw a man use a rifle to shoot at three people inside of a car.

Police arrived at the scene, but found only shell casings.

“The witnesses were inside, and that’s when they heard the commotion outside,” explained Sgt. Kevin Perlich with the Richardson Police Department on Thursday. “They saw none of these individuals or that individual who was doing the shooting inside the restaurant prior to the shooting itself.”

Then, about 15 minutes later, there were reports of another shooting in Dallas. Police said that the three victims drove southbound down to Fitzhugh Avenue, where they crashed out. According to investigators, there is a good chance that more shots were fired as the victims drove to this location.

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Two victims were taken to Baylor Medical Center at Dallas and the other victim went to Parkland Hospital. All three of these people are expected to survive, but Perlich said that the Parkland Hospital patient suffered more serious injuries. Their names have not yet been released.

A traffic camera belonging to the Texas Department of Transportation captured two of the victims being loaded into an ambulance early Thursday morning.

Investigators first focused their attention on the maroon 1989 Chevrolet Caprice that the victims were driving. The car had several bullet holes, and there were more shell casings and pieces of broken glass littered along the ground nearby. Meanwhile, police in Richardson were investigating at the IHOP restaurant until late Thursday morning.

Detectives are still not clear about the identity of the gunman or the motive for the shooting.

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The southbound Central Expressway service road was shut down Thursday morning so that authorities could conduct their full investigation. It has since been opened back up to regular traffic.