Dallas police said Tuesday early tests connect a former Utah state trooper to Monday's series of rush-hour shootings in Garland and Dallas.

Two people were killed and another was injured in the shootings Monday evening.

Dallas police said they think Brian Smith, 37, a former Utah trooper who shot himself early Tuesday morning during a standoff in Garland, shot and killed a big-rig driver in Dallas. They declined to comment on the other death in neighboring Garland because it was outside their jurisdiction.

"I certainly believe that he is going to be linked to the Dallas offenses -- the three shootings that occurred in the city of Dallas," Dallas police Lt. Craig Miller said. "Right now, I can't definitely say that he's involved in the Garland shooting."

Smith died Wednesday night from a self-inflicted gunshot wound. Police said he shot himself in the head early Tuesday morning after a brief standoff with police more than six hours after the shooting spree ended.

Smith had been stopped by Garland police on outstanding robbery and burglary warrants. Authorities said police did not know at the time that he may be connected to the highway shootings.

Miller said preliminary ballistics tests connected Smith to the killing in Dallas because the bullets from the standoff were a match. The weapon was a high-caliber semiautomatic handgun, Miller said.

"We feel safe in saying (Smith) ... was the shooter," he said.

Garland police spokesman Joe Harn said his department has not been able to make a definitive connection between Smith and the killing there, but acknowledged that he fit the description of the highway shooter: a balding, 40ish white man.

"We certainly hope it is him," Harn said. "But we are going to have to see more concrete evidence."

Garland and Dallas police expect more definitive test results on Wednesday.

The first shooting occurred at about 5:45 p.m. Monday in Garland. A pickup truck pulled up alongside Jorge Lopez, who was stopped at a red light, and began shooting, police spokesman Joe Harn said. Lopez, 20, was killed.

"It looks like he was just simply stopped here at the red light; someone pulls up and fires several rounds and shoots him," Garland police officer Joe Harn said.

Witnesses told police the pickup then drove away toward Interstate 635, where the driver of an 18-wheeler was shot at shortly after. The driver of that big rig was not injured.

From there, police say the gunman continued driving westbound on the highway where he shot at William Miller, the driver of a United Van Lines big-rig, near Royal Lane. The rig driver, William Miller, died at the scene, Dallas police Sgt. Gil Cerda said.

Investigators said the same driver fired at a third 18-wheeler about a quarter-mile down I-635 near Plano Road in Dallas minutes later, but missed. The driver of the tractor-trailer, Gary Roberts, was injured by debris and glass and needed several stiches, but he was out of the hospital Tuesday, police said.

While he was being shot, Roberts radioed his terminal manager, Jesse Medford, with Dugan Truck Line.

"I'm getting shot at," he told Medford. "I think I'm shot."

After telling the Roberts to pull over, Medford said he called 911. Roberts told him that he did not know who was shooting and could not give a detailed description of the assailant.

"He didn't say anything about any type of road rage," Medford said.

"Whoever this person may be, he is obviously upset with something or someone and he's taking it out on innocent victims going down the road," Cerda said.

The shootings shut down westbound LBJ Freeway for most of the night. Traffic was still backed up shortly before 9 p.m. but was moving freely by 10 p.m.

The 42-year-old truck driver from Kentucky was about to drop off his big rig and fly home to be with his wife and children for the Christmas holiday.

Lt. Craig Miller, of the Dallas police, said the driver's actions were "heroic" because he was able to control his truck despite suffering deadly wounds.

Schepps Dairy is offering a $10,000 reward and Crime Stoppers will pay an additional $10,000 for information leading to an arrest and indictment in Miller's murder.