DALLAS — He served his country overseas. Then he came home, became radicalized, and turned into a mass murderer.

Micah Johnson, 25, of Mesquite, Texas, was identified by police as the sniper who shot 12 people during a Black Lives Matter protest in downtown Dallas on Thursday night. By Friday, the authorities had found “bomb making materials, ballistic vests, rifles, ammunition, and a personal journal of combat tactics” in the Army veteran’s apartment—evidence suggesting that the killings might have been only one part of Johnson’s violent plans.

Johnson left the Army “under a cloud of sexual harassment charges made by a fellow soldier who sought an order of protection against him and said he needed mental health counseling.” And on social media, Johnson left traces of a militant mindset. Johnson’s profile photo on Facebook shows him in a dashiki, holding a clenched fist in the air. Johnson’s cover photos are a black liberation flag and a black power fist.

Dallas police chief David Brown said Johnson told police “he was upset about the recent police shootings” and “wanted to kill white people, especially white officers.” Activists at Thursday’s night Black Lives Matter march, however, said that the shooter behind the deadliest day for American law enforcement since the 9/11 attacks was not part of their protest. Three other suspects were taken into custody but Johnson is believed to have acted alone. Five officers are dead and six others are seriously wounded, in addition to one civilian.

Johnson did not explicitly identify himself as a member of the Nation of Islam, a militant black Muslim group, but liked pages relating to Elijah Mohammed, the group’s deceased founder. Johnson also liked several militant and black separatist groups such as The New Black Panther Party and the African American Defense League.

The league posted on Facebook after Johnson’s massacre: “ATTACK EVERYTHING IN BLUE EXCEPT THE MAIL MAN, UNLESS HE IS CARRYING MORE THAN MAIL.”

Johnson also liked the Black Riders Liberation Party, which describes itself as a “new generation” of Black Panthers.

“We need recruits everywhere!” one of the group’s leaders posted on Thursday before the Dallas shooting. “Arm yourself or Harm yourself!”

The advertisement for the new group was accompanied by a photo of armed men.

Johnson already had some familiarity with weapons. He served as a private first class in the Army Reserve and deployed to Afghanistan in November 2013 as a carpenter. He served at Bagram Air Base, the largest U.S. base there, before returning in July 2014.

His deployment was apparently cut short, though, when he was accused of sexually harassing a female soldier in May 2014. The Army sent him home and recommended an “other than honorable discharge,” according to the military lawyer who represented him. In a court filing, the alleged victim said she wished Johnson would get “mental help.”

Those who knew Johnson told the Dallas Morning News that he was obsessed with military-grade weaponry and wanted to join the armed forces since high school, where he was a member of the Junior Reserve Officer Training Corps (JROTC). Neighbors said it appeared Johnson was doing military-style training exercises on his property leading up to the attack.

In Johnson’s home town of Mesquite, 20 miles west of downtown Dallas, the manicured lawns and tree-lined streets swarmed with reporters on Friday, as neighbors came to terms with the tragedy.

In the quiet neighborhood of Pecan Creek, The Daily Beast spoke with 19-year-old Israel Cooper. He used to play basketball with Johnson, who they called “X.” Playing weekly games for the past two years at the court around the corner at Jay Thompson Elementary School, Cooper described his relationship with Johnson as “friendship by accident.” They last played ball just a week ago, at which time Cooper said he mentioned the Black Lives Matter movement.

“He was just a pretty cool guy. He had good vibes. I don’t know how this happened. I was in shock.” Cooper described Johnson as “not very political,” but “educated.”

“It’s the quiet ones that just do the most devastating stuff. You never see it coming, but then it’s more expected, like, I should have known… People’s that’s more often quiet, you never know what they’re thinking,” Cooper continued, arms crossed and eyes wide.

On hearing the news about Johnson, Cooper said “I wasn’t angry or sad… because a man knows what he’s doing. That’s a grown man. And there are consequences.”

Though Cooper admitted he frequently felt profiled and unsafe as a young black man in a white neighborhood, he empathized with both the police department as a whole and the victims on Thursday night’s massacre. “Yeah, I do feel for the officers, because just like him they’re men too. They have to come home to a family… All white cops are not bad cops.”

When asked about the affect of the shooting, Cooper said he felt it put black people even more in fear for their lives.

Neighbor Edabrina Williams, who has lived in Pecan Ceek for 12 years, is a mother of four girls between the ages of 7 and 28. She came out to speak with us because she is worried about the future for her own children. “I’m scared if they get pulled over,” she said. “It’s not like getting stopped five or 10 years ago…

“It’s because of the persona the police officers have put in front of the world. They have a gun, and they can shoot. It doesn’t make it right to shoot an unarmed person just because of the color of their skin.”

Williams, surrounded by other neighbors, summed up what seemed to be the common consensus, her peers nodding along: “There’s a lot of distrust with the police right now. Instead of protecting and serving like it’s originally supposed to have been, it’s like kill at any cost, or kill if you feel a certain way. It’s not right.”

Though she did not know Johnson well, she speculated that he, like many young men in the community, was tired of the way things have been. “Maybe he was trying to wake up the world.”

José Moore, the sole white neighbor The Daily Beast found walking the neighborhood on the somber summer afternoon, is a Holocaust survivor that has lived in Mesquite for seven years after moving from Holland. She described watching Johnson running on a few occasions. “I would say hello, but he would not answer back because of my color. I would say he was prejudiced… I think that they’re not all that friendly in this neighborhood, but I love people no matter what their color.”

Though racial tensions remained today in the streets of Mesquite, the violence diluted differences with a visceral shock and sadness.

“We’ve been there. We’ve been on thin ice,” said Edabrina Williams, “but never did I imagine that it would happen right here in Dallas.”

Johnson’s sister, Nicole, spoke out on Facebook after her brother was identified.

“The news will say what they think but those that knew him know this wasn’t like him. Only close family can call me. This is the biggest loss we’ve had,” she wrote.

Johnson’s anti-cop sentiment was shared by his sister on Facebook. Two days before the massacre, she posted an ominous message about police being harmed.

“Everything coming into the light and I for one think these cops need to get a taste of the life we now fear.”

Johnson formerly attended the “self-defense and personal protection” gym Academy of Combat Warrior Arts in Richardson and Fort Worth, Texas, gym owner and CEO Justin Everman told The Daily Beast. The gym’s Twitter account says it provides “reality based training for today’s Urban environment.”

Along with more traditional martial arts classes, the gym also teaches seminars in “Urban Everyday Carry and Improvised Weapons” and “Weapons Defense.” Everman said many of the gym’s members are police officers and stressed that “we have completely no affiliation with him whatsoever.”

“It’s disgusting, what he did,” he said. “I’m disgusted.”

—with additional reporting by Kate Briquelet and Nancy A. Youssef.

Updated: July 9, 2016, 7:30 a.m.