Brian Smith, 37, had been in critical condition on life support from a self-inflicted gunshot wound. Police said he shot himself in the head Tuesday, more than six hours after the roadway shooting spree ended.
Authorities were working to confirm that Smith was the gunman in separate fatal shootings minutes apart Monday on a Garland street and a Dallas interstate, Dallas police Lt. Craig Miller said.
Earlier Wednesday, police shut down the freeway to re-examine the scene of one of the shootings. "It's just another thing that's part of the investigation," Miller said. "It's not a critical component. That's what we wanted to do, just check everything we can."
Dallas police said they think Smith was responsible for at least one death that resulted from the shootings. Garland police were trying to verify that the gun Smith used on himself was the same used in another man's death.
Both were waiting for ballistics tests to come back for possible matches of bullet casings.
Warrants for Smith's arrest had been issued in the Fort Worth suburb of Southlake, where authorities have obtained evidence linking him to two robberies in the past eight days. Both incidents involved thefts in which purses were stolen from women in vehicles parked at businesses near where Smith lived.
Police linked Smith to the incidents through witness identification and video of him using a credit card belonging to one of the victims, Southlake police spokesman Mike Bedrich said.
Smith moved to Keller with his wife and children last spring, just months after his conduct came under scrutiny from the Utah Highway Patrol. His peace officer certification was revoked after he went on a drinking binge and threatened to kill himself, according to a report by the Utah Peace Officer Standards and Training investigations bureau.
Smith's friends and neighbors struggled to make sense of the case.
In Utah, he was remembered as a good father who never lost his temper and coached youth soccer and basketball.
"This is a shock for everyone who knows Brian," said Michael Peterson, Smith's former bishop in the Mormon church. "Obviously, he was struggling with some things. But the Brian Smith that everyone around here knows would never have done any of these things."
Karen Baughman, a neighbor in Keller, said Smith and other members of his family showed up on her doorstep on Sunday with Christmas cookies they'd brought home from church.
"He was just hanging Christmas lights two weeks ago," she said. "I mean, this is dumbfounding."
The shootings Smith was suspected in began around rush hour Monday in Garland at a major intersection. A motorist pulled up alongside a small Nissan and shot and killed the Nissan's driver, 20-year-old Jorge "George" Lopez of Rowlett, Garland police spokesman Joe Harn said.
Three semitrailer drivers were later shot at on Interstate 635, and one of them died. William Scott Miller, a 42-year-old married father of two from Frankfort, Ky., was on his way to get on a plane to go home to his family for the holidays.
Harn said Garland police are still waiting for tests to determine if the gun Smith used on himself is the same one used in Lopez's death.
"I can tell you this: There's nothing telling us so far that it's not him," Harn said.