GARLAND (Texas) • There was a time when he was known as a well-mannered young man - a regular at his church and a pleasant presence on a tree-lined, suburban, multicultural street in a neighbourhood called Camelot. He grew up to serve his country in Afghanistan.
But last Thursday night, 25-year-old Micah Johnson, an African-American, drove his car to a rally against police violence and began killing officers in downtown Dallas, hoping to single out the white ones.
In the process, he also managed to bring his war back home, killing five officers and wounding seven others, as well as two civilians,
New details on Johnson's life revealed a young man who had returned in disgrace from his stint abroad in the Army Reserve due to sexual harassment charges, but continued a training regimen of his own - devising and conducting military-style exercises in his backyard and reportedly joining a gym that offered martial arts and weapons classes.
A Dallas County official also revealed that Johnson - who was killed by police using a robot-delivered explosive device - had kept an extensive journal and described a method of attack in which a gunman fired on a target and then quickly moved to another location to confuse an enemy.
Although it did not seem to be a precise plan for Johnson's ambush, it was strikingly similar to the tactics he used.
"It's talking not only about how to kill but how to keep from being killed," said Mr Clay Jenkins, Dallas County's chief executive and director of homeland security and emergency management. "It shows that he was well prepared."
Mr Jenkins, who said he heard descriptions of Johnson's journal from other officials, said there were details of "shoot and move" tactics - ways to fire on a target and then move quickly and get into position at another location to inflict more damage on targets without them being able to ascertain where the shots are coming from.
This tactic is used by the military's special forces.
"It appeared that he was an excellent marksman and was calmly shooting, as opposed to someone who's just holding a gun up and aiming it and pulling the trigger in the direction of where they think people are," said Mr Jenkins.
He added that Johnson had used a semi-automatic SKS rifle and a high-capacity handgun. He drove his vehicle to the demonstration and parked it, but was on foot at many points throughout the attack.
His knowledge of "shoot and move" - and the fact that a few of the protesters in the crowd who were not involved in the shooting were armed and carrying rifles - has helped shed light on how a theory of multiple assailants emerged.
Johnson opened fire at the end of a march by hundreds of demonstrators decrying the fatal shootings by police of two black men earlier last week. Johnson had shown an affinity for radical black-power organisations on his Facebook page. Organisers of the Black Lives Matter network and others have denounced the shooting spree.
A neighbour had seen Johnson doing military-like exercises in his backyard in Mesquite in the last couple of weeks.
Johnson had also attended a "self-defence and personal protection" gym, the Academy of Combative Warrior Arts in Richardson, Texas, gym owner Justin Everman told The Daily Beast.
The gym teaches martial arts classes and gives seminars such as "urban everyday carry and improvised weapons" and "weapons defence".
Mr Courtney Williams, a 37-year-old electrician, said he had known Johnson during his teenage days. He remembered Johnson as a "well-mannered" youth who was active in church events.
"He was just a quiet kid," he said. "No attitude, no trouble with school. Just a normal kid."
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