But friends said he was dissatisfied, and the marketing-manager-turned-hairdresser began to take an interest in law enforcement, influenced in part by one of his neighbors, an Arlington police officer.

Image Officer Brad Miller, of the Arlington, Tex., police, was fired in the shooting death of an unarmed student-athlete. Credit... Arlington Police Department

“He was kind of a guy that was searching for his direction,” said the Rev. Gary Smith, the senior pastor at Fielder Church in Arlington and a friend of Officer Miller, who used to trim the pastor’s hair at the now-closed RazlDazl. “He watched his next-door neighbor and saw the impact he made for good as a policeman and that was one of the things that drew him to that. He wanted to be a guy who did more than sell widgets. He wanted to make a difference.”

In the early morning hours last Friday, Officer Miller ventured into a fast-paced encounter with a burglary suspect in a car dealership that left the suspect, an unarmed college football player, dead. That led to Officer Miller’s dismissal from the force and put him in the center of public scrutiny, criticism and outrage.

He had his state peace-officer license a mere 19 weeks and was two hours shy of completing his field training when he shot 19-year-old Christian Taylor to death after Mr. Taylor vandalized a car and broke into the dealership. Beyond his eclectic work life, he had known both sides of the law in a way few officers ever do.

Two months before the shooting, his father-in-law, Lester Leroy Bower, who spent three decades on death row for murdering a sheriff’s deputy and three other men, was executed in the state’s death chamber in Huntsville. He had two daughters, and was represented at their weddings by a candle, according to an article in The Dallas Morning News about the Bower family. Officer Miller did not attend the execution in June, but his mother-in-law did.