(CNN) -- A former Utah policeman is a suspect in at least three of Monday's four rush-hour shootings near Dallas, Texas, including one of two fatal attacks, police said Tuesday.

CNN affiliate KSL in Salt Lake City, Utah, provided this file photo of the Dallas suspect, Brian Smith.

The suspect, Brian Smith, tried to commit suicide after the Monday-evening shootings and was in a hospital in serious condition, Dallas police detective Lt. Craig Miller said.

Police used ballistic tests to link Smith, a Utah state police officer for 12 years, to the shootings in which one driver was killed, one was injured by shattered glass and one escaped uninjured, Dallas police detective Lt. Craig Miller said.

Miller said it is unclear if Smith was involved in the other fatal shooting, which was the first attack of the evening.

Four motorists were attacked along a three-mile stretch near and on the LBJ Freeway, about 10 miles northeast of downtown Dallas, on Monday evening, police said.

The first attack, which happened in Garland, Texas, about 5:41 p.m., killed Jorge Lopez. Garland police said Lopez, 20, was sitting in his Nissan at a traffic light when a man in a pickup pulled alongside him and fired shots into his car, killing him.   A few minutes after the Garland shooting and two miles away on LBJ Freeway, a gunman fired at two tractor-trailers.

While one driver escaped injuries, William Scott Miller, 42, of Frankfort, Kentucky, was shot to death behind the wheel of a United Van Lines truck, police said.

"He was going to be traveling home," Craig Miller said. "He was about to park his rig. He was going to get on a plane to fly to be with his wife and children for the Christmas season and then come back to this location."

Miller called the truck driver a hero, saying he was able to control his rig before he died -- preventing other motorists from being hurt.

The fourth attack came a mile west on LBJ Freeway when gunfire shattered the windshield of another tractor-trailer. The bullets missed the driver, but flying glass caused minor cuts, police said.

Miller said video from the Garland shooting is available, and specialists were trying to enhance it to bring out details. Businesses along the other routes also may have video that will help police, he said.

A friend of Lopez's said he was "a straight-up good guy, never had problems with anybody, never started anything with anybody."

"So that's why this seems so out of the blue," Lopez's friend said.
What condition is the suspect in? Who was named a suspect? What did the suspect try to do? Where were the drivers injured? Who was shot and killed? When were the shootings? Who did the suspect try to kill?
serious Brian Smith. commit suicide near Dallas, Texas, William Scott Miller, Monday-evening Four motorists
question: What condition is the suspect in?, answer: serious | question: Who was named a suspect?, answer: Brian Smith. | question: What did the suspect try to do?, answer: commit suicide | question: Where were the drivers injured?, answer: near Dallas, Texas, | question: Who was shot and killed?, answer: William Scott Miller, | question: When were the shootings?, answer: Monday-evening | question: Who did the suspect try to kill?, answer: Four motorists