The lone gunman and Army veteran who killed five Dallas law enforcement officers in an apparent rage over the deaths of black people at the hands of white police had been increasingly exploring black nationalism even as he compiled a thick journal of combat-style techniques.

Babu Omowale, a co-founder of the Texas city's People's New Black Panther Party, said Micah Xavier Johnson had attended several meetings of the black nationalist group but had never been to the group's armed gatherings. "We had no idea what the brother's mentality was," said Omowale.

"He was just someone searching for knowledge about himself, like most young people searching for how they can change this world for the best," said Akwete Tyehimba, who met Johnson in May, when he went into her shop, Pan-African Connection. It is a Dallas bookshop and African-arts store where like-minded activists gather.

"We had just a very brief conversation, but he was a nice young man," Tyehimba said, and one who carried himself with strength and confidence. "He fit right in."


Now, Tyehimba, 53, wonders whether the older activists could have swayed the 25-year-old from his bloody path. "I just wish we had a chance to get to know him and guide him."

Along the way, Johnson was quietly putting together a "voluminous" journal "filled with combat-type tactics" that investigators recovered from his home, said Judge Clay Jenkins, Dallas County's chief executive. The journal shows that Johnson, who served in Afghanistan but never saw combat, extensively studied what is described as a "shoot and move" combat tactic. "It's a concept of wanting to move from vantage point to vantage point, without being pinned down in one location, to inflict as much damage as possible," Jenkins said.

Johnson's journal was key in leading investigators to think that he acted alone, Jenkins said. Initially, because gunfire appeared to have come from multiple locations, hitting people at different angles, authorities thought more than one assailant could have been involved.

"The verified reports and evidence we were getting indicated that there were shooters firing from different locations," Jenkins said. "But [it is] very probable that when he was telling police that he acted alone, he was telling the truth."

During a search of Johnson's home in Mesquite, detectives said they found bomb-making materials, ballistic vests, rifles, ammunition.

Reports of Johnson's association with black nationalism and the killings baffled friends, former colleagues in the Army and others who knew him. "He was my friend. He was never racist," said Julius Young, a classmate of Johnson's in Mesquite, a Dallas suburb. "That was not that type of dude."

"Micah was my very close friend. I refuse to remember him as anything less," a former classmate, Stanlee Washington, wrote on his Facebook page. In Mesquite, Avis Blanton has lived next door to the Johnsons for more than 12 years. "He was a good kid. He was truly, truly good," she said.

On his own Facebook page, Johnson posted an image of a fist with the text "Black Power". He also expressed interest in the People's New Black Panther Party, which the Southern Poverty Law Centre describes as a "virulently racist and anti-Semitic organisation".

Young said that since Johnson had been home from deployment in Afghanistan, where he served in 2013 and 2014, he and his friends talked about sports, women and family issues - but never the issue of black people dying at the hands of police.

While he was in Afghanistan, a female soldier in his unit accused Johnson of sexual harassment. She said Johnson required "mental health" help, according to Bradford Glendening, a military lawyer who represented Johnson.

Four of the five slain officers had served in the military.

Those who knew Johnson from the military expressed harsher feelings in their Facebook posts. Luis Cantu wrote on Facebook: "We all knew he was off but I had no idea he was capable of this. He was a recluse but every now and then he would come out and make waffles for us with his waffle maker. Goes to show you that you don't always truly know somebody or what they are capable of."