GARLAND, Texas (AP) -- Police say the gun a former Utah trooper used to kill himself has been linked to the death of a second motorist in Texas last month and two other highway shootings.

Police in the Dallas suburb of Garland said Tuesday preliminary tests show Brian Smith's weapon killed 20-year-old Jorge Lopez at a red light Dec. 22.

Dallas police said subsequent shootings on Interstate 635 that same night also match Smith's weapon. No one was hurt.

The gun already had been linked to the fatal shooting of truck driver William Scott Miller on the interstate around the time of the other shootings.

Smith shot himself after a brief standoff with police. He died Dec. 24 after he was taken off life support.