Dallas police on Friday identified 25-year-old Micah Xavier Johnson as the lone gunman in the killing of five Dallas police officers . The attack Thursday evening, which occurred during a Black Lives Matter protest, also injured seven other police officers and two civilians.

Johnson was killed after police detonated a bomb strapped to a robot . He had no known criminal history, officials said Friday, but cops found material to make bombs , rifles and ammunition in his home.

Johnson had been a private first class in the Army Reserves, a military spokeswoman confirmed. He enlisted in 2009, was deployed to Afghanistan in November 2013 and returned in July 2014, receiving several awards for his service. He left the military in April 2015.

CBS said that he lived in Mesquite, Texas , a suburb of Dallas.

Police Chief David Brown said Johnson wanted to kill white people, especially white officers. Officials said he was upset about the recent deaths of two black men at the hands of law enforcement.

Authorities said that some people identified Johnson as a loner during their ongoing investigation. They have not found any evidence that Johnson was linked to any political groups or the Black Lives Matter movement, The New York Times reported .

Israel Cooper, a friend of Johnsons, told The Associated Press that Johnson wasnt really political , despite being educated. When he heard that his friend was a suspect, he couldnt believe it, he said: Johnson wasnt a violent or rough dude and had a good vibe.

Cooper said the last time he saw Johnson was about a week ago, but that the two often played basketball near Johnsons home.

The attack on Dallas police officers marked the deadliest day for law enforcement in the United States since Sept. 11, according to the National Law Enforcement Officers Memorial Fund , a group that tracks and memorializes officer deaths.

Following the shooting, according to Brown, officers cornered Johnson in a parking garage at El Centro College in downtown Dallas. Brown said officers negotiated with him for several hours. At one point, Brown said that Johnson told police negotiators that the end is coming and hes going to hurt and kill more [law enforcement officers]. Johnson also claimed that there were bombs in the garage and the downtown area.

Talks eventually broke down and an exchange of gunfire ensued between Johnson and the officers, Brown said, at which point officers felt they had no other choice but to deploy a robot equipped with an explosive device. They detonated it while Johnson was still cornered.

As reported elsewhere, Johnson did receive some training at the Academy of Combative Warrior Arts -- but some outlets mischaracterized that training as related to shooting on the move. The academy is a martial arts and self-defense training center that specializes in hand-to-hand combat.

Johnson worked nearby in the suburb of Richardson and stopped by the academy several times about a year and a half ago, the academys founder told The Huffington Post.

All we did was teach him hand-to-hand. Thats it, said Justin J. Everman. There was no firearms training that he did with us whatsoever.

He couldnt recall Johnsons demeanor when he trained there, but also didnt remember seeing anything out of the ordinary. The academy also trains students to attempt to de-escalate before fighting.

Our goal is to get people home safe at night, Everman said. If your wife is coming out of the business at night and going to her car, were trying to give her a toolset to defend herself.

Andy Campbell contributed reporting. This article has been updated to include details on the confrontation from the police department and information about Johnsons martial arts training.

READ MORE ON THE DALLAS POLICE MASSACRE

• Sniper Attack Leaves 5 Police Officers Dead, 7 Injured In Dallas
• These Are The People Killed And Injured In The Dallas Attack
• Obama Says Dallas Police Shooting Despicable, Highlights Need For Gun Control
• Eyewitness Captures Moment Dallas Protest Turned From Calm To Chaos
• Witnesses Record Horror Of Dallas Attack
• A Dallas Cop Saved This Mans Life As The War Began
• Former NYPD Detective Gets Emotional Over Dallas Shooting
• Woman Who Filmed Dallas Shooting Was Terrified And Confused
• Pretty Much Anyone In Texas Can Openly Carry A Weapon Of War
• New York Post Recklessly Hypes Civil War After Dallas Shooting
• In The Face Of Violence, Dallas Police Vow To Continue De-Escalation Tactics
• Dallas Shooting Eyewitness Says Exactly What We Need To Hear After This Week
• Hillary Clinton: White People Must Listen To Legitimate Cries Of Black People