The officer, Aaron Tolerton, is accused of being involved in a disturbance in Farmers Branch and lying to investigating officers.
A DPD internal affairs investigation found that "Officer Aaron Tolerton engaged in adverse conduct when he displayed a firearm in an alarming manner while off-duty, became involved in an incident which resulted in a police response and he was untruthful to the Farmers Branch Police Department."
Tolerton is charged with aggravated assault with a deadly weapon because Farmers Branch police say a woman called 911 back on March 28, saying he had threatened her with a gun. Sources tell FOX 4 that the woman was Tolerton's ex-girlfriend, and she was with her new boyfriend when the incident allegedly happened.
Sources also say Tolerton was off-duty but in uniform when the incident allegedly occurred.
He was not arrested at the time by Farmers Branch police, though they did respond to the location in the 5000 block of Galleria.
Tolerton's ex-girlfriend and her new boyfriend applied for a protective order after the incident, but that was denied by a Dallas judge.
FOX 4 called Tolerton's attorney for comment. He has not yet returned our call.
Tolerton is expected to appeal his termination.
On Feb. 11 of this year, a man named Desmond Luster was shot and killed by Tolerton, who was working off-duty as security at the Flying J truck stop near I-20 and Bonnie View.
Luster, who was in his pickup truck, had been chasing burglary suspects who ran from his home.
Tolerton saw Luster and said the truck was coming toward him at a high rate of speed. Tolerton opened fire on the truck, killing Luster.
Former District Attorney Craig Watkins represents Luster's family. He says the felony charge against Tolerton and the fact that he lied to investigators draws into question his truthfulness about the events surrounding the shooting of Luster.