The army veteran who shot and killed five police officers during a protest in Dallas on Friday had been sent home from Afghanistan after being accused of sexually harassing a fellow soldier.

Micah Xavier Johnson, who fatally shot five officers and wounded seven more before police killed him with a remote-controlled bomb, lived with family in the suburb of Mesquite, where he played basketball for hours at a time.

Friends said the 25-year-old didn’t seem interested in politics, but his Facebook page shows he “liked” black militant groups including the African American Defense League and the New Black Panther Party, which was founded in Dallas.

His profile photo showed him wearing a dashiki and raising his fist over the words “Black Power”, and his cover shot carried the red, black and green Pan-African flag.

For six years starting in 2009, Johnson served in the army reserve as a private first class with a specialty in carpentry and masonry, the military said. In May 2014, six months into his Afghanistan tour, he was accused of sexual harassment by a female soldier.

The army sent him back to the US, recommending an “other than honorable discharge”, said Bradford Glendening, the military lawyer who represented him. That recommendation was “highly unusual”, Bradford said, since counselling is usually ordered before more drastic steps are taken.

“In his case, it was apparently so egregious, it was not just the act itself,” Glendening told the Associated Press.

According to a court filing Glendening read over the phone on Friday, the victim said she wanted Johnson to “receive mental help”, while also seeking a protective order to keep him away from her and her family, wherever they went. Johnson was ordered to avoid all contact with her.

Glendening said Johnson was set to be removed from the army in September 2014 because of the incident, but instead got an honorable discharge months later. “Someone really screwed up,” he said. “But to my client’s benefit.”

When authorities searched Johnson’s home on Friday they found bomb-making materials, ballistic vests, rifles, ammunition, and a personal journal of combat tactics.

The Dallas police chief, David O Brown, said Johnson told negotiators before he was killed that he was acting alone and was unaffiliated with any group. The chief said Johnson cited the fatal shootings of black men by police officers in Louisiana and Minnesota, which prompted the protest march in Dallas and many other cities.

“The suspect said he was upset with white people and wanted to kill white people, especially white officers,” Brown said. Activists with Black Lives Matter, whose peaceful march police were guarding as he opened fire, repudiated the shootings, and it wasn’t immediately clear if Johnson had any connection to the movement, which has disavowed violence.

But one of the groups Johnson “liked” on Facebook, the African American Defense League, posted a message earlier in the week encouraging violence against police in response to the killing in Louisiana.

“The Pig has shot and killed Alton Sterling in Baton Rouge, Louisiana! You and I know what we must do and I don’t mean marching, making a lot of noise, or attending conventions. We must ‘Rally The Troops!’ It is time to visit Louisiana and hold a barbecue.”

The message was attributed to Dr Mauricelm-Lei Millere, a leader in the organisation.

Another group Johnson “liked” was the New Black Panther Party, whose leaders have “long expressed virulently anti-white and antisemitic opinions,” according to the Southern Poverty Law Center. Johnson also “liked” the Nation of Islam and the Black Riders Liberation Party, which the center describes as “hate groups”.

Among Johnson’s other social media likes were groups that focus on the history and accomplishments of African-Americans, such as Black Love Matters, the Nubian Rootz Cultural Center, and I Love Black Archaeologist, a web series whose main character uses a time machine to visit famous black people.

The Dallas police department said Johnson’s Facebook account also included information about Richard Griffin, also known as Professor Griff, who “embraces a radical form of Afrocentrism”.

On his Facebook page on Friday afternoon, Griffin, a member of Public Enemy – an influential hip hop group known for its politically charged lyrics – said he does “not advocate killing cops”. Johnson had no criminal history, according to authorities. Local court records show his parents were divorced in 1996.

He was believed to have shared a two-storey tan brick home in Mesquite with family members. He graduated from John Horn high school in Mesquite, where he was a Reserve Officers’ Training Corps member, school district officials said.

Sharon Carter, who works in the district’s registrar’s office and lives near Johnson’s home, said she saw him occasionally wearing military fatigues as he left for army reservist training, but never saw him armed.

“They say he was standoffish in high school,” Carter said. “I never really spoke to him. He kept to himself.”

A relative had praised Johnson on his birthday in 2014 as “definitely army strong” on his Facebook page, calling him an “entertaining, loving, understanding, not to mention handsome friend, brother (and) son”.

After Johnson was killed, a relative posted on her Facebook page: “I keep saying its not true … my eyes hurt from crying. Y him??? And why was he downtown.” She did not respond to Facebook messages.

Friend Israel Cooper said Johnson was known as Xavier, his middle name, had a “cool vibe”, wasn’t really political and seemed educated. Cooper said he and Johnson played basketball at a park near his home. “He would be out there for eight hours. Like it was his job. Just hoopin’,” he said.

Cooper said that when he heard the suspect was Johnson, he “was in disbelief because he’s just not like a violent or rough dude”.