DALLAS » Micah Johnson’s journal opened a portal into a madman’s mind.

In handwritten scrawls and crude sketches, police learned about the 25-year-old’s gun lust, his fascination with shoot-and-scoot tactics, and increasing interest in black nationalism.

But his writing also showed something else, according to a Dallas Police Department officer with access to evidence in the investigation.

His words aren’t an intricate manifesto. They were fleeting thoughts that bounced around inside a brain that never really grew up.

On Sunday, three days after he slaughtered five Dallas police officers and wounded seven others and two civilians in a rampage fueled by racism and rage, a more nuanced portrait of the killer began to take shape.

His journal included riffs about assault rifles, but they were interspersed with rap music lyrics. A dispassionate sentence about ways to inflict maximum carnage, might be followed by one with complexity and heart, about being both African and American during a time where those identities often seem to conflict.

“This guy might have been a loner,” said the officer, who requested anonymity because he isn’t authorized to speak publicly about the case. “But he was smart.”

Dallas Police Chief David Brown said Sunday morning on CNN’s “State of the Union” an injured Johnson wrote the initials “R.B.” on the walls of the downtown parking garage where he was barricaded last week.

Brown later ordered officers to use a remote-controlled robot armed with explosives to kill Johnson.

The investigation suggests Johnson had long prepared for the attack, according to the chief, but fast-tracked his plans after the march protesting the recent fatal police shootings of two black men in Louisiana and Minnesota was announced.

Brown said police are “convinced this suspect had other plans and thought that what he was doing was righteous” and was determined to “make us pay for what he sees as law enforcement’s efforts to punish people of color.”

But the police official close to the investigation who spoke to The News said Johnson’s written ramblings did not contain a direct threat or outline definite plans.

Johnson “was studying all these different disciplines and you can’t make heads or tails out of it,” he said.

Brown did not return recalls from several reporters from The News on Sunday. But he told CNN that police are still analyzing the Army veteran’s laptop and cell phone to figure out whether other people helped Johnson plan the ambush after a peaceful march through downtown Dallas.

Johnson was in JROTC at John Horn High School in Mesquite and enlisted in the Army reserve shortly after he graduated in 2009. He also enrolled for four classes at Richland College in the spring of 2011, but did not complete any of them, the school said.

He served in Afghanistan, but was discharged last year after being accused of sexual harassment, according to his attorney.

Those who knew Johnson in the Army say they don’t recognize the pathologically violent racist described in news accounts.

He openly spoke of his Christian faith in Afghanistan and often chose to socialize with white soldiers.

“It’s not racism guys,” Heather Brooks wrote on Facebook. “Hate what he did, but don’t hate the man … it was mental sickness unchecked and untreated. He had good in him, we all know he did.”

Brooks, of Odessa, declined to comment when reached by phone.

“If you didn’t hang around him then you wouldn’t understand him,” said a black soldier who served in the same unit with Johnson. “He wasn’t weird, he wasn’t off, he was goofy. He was almost like a class clown.”

But he said the military’s sexual harassment investigation curdled his friend’s good humor.

“He just wasn’t as talkative,” the soldier said of Johnson. “He lost his funny spirit.”

He said it probably never occurred to Johnson that the cops he fired on included his brothers and sisters who had served in the military.

Other friends said Johnson showed little interest in conversations about racial injustice or the shooting of Trayvon Martin.

Soldiers wondered out loud whether the stress of serving in a combat zone got to their friend. Mortars exploded in the area four or five times a day.

Back in the states, a former co-worker said Johnson seemed “very affected” by officer-involved shootings of black men in recent years — something he told police before negotiations failed.

Johnson also told police he had been training for the deadly ambush. A neighboring family said he performed what looked like military training exercises in his yard.

Johnson took self defense classes at the Academy of Combative Warrior Arts in Richardson for six months to a year.

Justin Everman, who owns the business, said the classes only involved hand-to-hand defensive measures, nothing related to weapons training.

He said Johnson’s round of classes ended more than a year ago.

Everman denounced the shootings, which he called atrocious.

“We are very depressed,” he said. “It’s just disgusting.”

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(This story was written by Scott Farwell. It was reported by Farwell, Brittney Martin, Brandon Formby, Jennifer Emily, Brandi Grissom, Holly K. Hacker, Katie Leslie and Christine Schmidt.)

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©2016 The Dallas Morning News