The suspect was last seen Monday evening heading west on Interstate 635, a loop that goes around Dallas and connects to other interstates, said Sgt. Gil Cerda, a Dallas police spokesman.
The shootings happened within minutes of each other. Afterward, rush hour traffic slowed along the highway as police shut down all westbound lanes of 635 east of the shooting scenes for several hours.
Police had a few witnesses after the shootings and were hoping to contact more. "We've got detectives working," Cerda said.
The first shooting occurred around 5:45 p.m. Monday in Garland, a Dallas suburb. A pickup truck heading south on a major road pulled up alongside a small Nissan stopped at a red light and began shooting, police spokesman Joe Harn said. The Nissan driver was killed.
Witnesses told police the pickup then drove off toward I-635 in Dallas, where an 18-wheeler was shot at shortly after. The driver was not hit, but the windows on the vehicle were shattered by the bullets, reports CBS station KTVT. The driver was taken to an area hospital to be treated for non-life threatening injuries.
The suspect continued west on the highway, then shot and killed the driver of a United Van Lines 18-wheeler rig, Cerda said.
Then the suspect drove about a quarter- to a half-mile on the interstate and fired at another 18-wheeler. The driver was injured by debris and glass but not struck by a bullet.
"I'm getting shot at! I think I'm shot!" the driver told Medford.
After telling the driver to pull over, Medford said he called 911. The driver told him that he did not know who was shooting and could not give a detailed description of the assailant, Medford said.
"He didn't say anything about any type of road rage," Medford said.
Police are looking for a suspect described as a balding white man in his 40s, driving a tan Ford F-150 extended cab pickup.
The driver killed in the first shooting was identified as 20-year-old Jorge Lopez, of Rowlett. The identity of the rig driver who was killed was not immediately available.