The Dallas shooter was 'ostracized' by black power groups before he opened fire on police officers in Dallas

New details have emerged about Micah Xavier Johnson, the man who shot twelve police officers in Dallas last Thursday, killing five.

In an interview with The Blaze, Johnson's parents and stepmother said his behavior changed noticeably after he left the US army in 2014. Johnson served six years in the military, including a seven-month deployment in Afghanistan.

Johnson wanted to become a police officer growing up, according to his mother, Delphine. He became enthusiastic about joining the military and "wanted to protect his country."

But during his service, Johnson's idealistic view of the government turned resentful. His family can't trace the change to a single incident, but they contrasted the extroverted personality of his youth to his more recent state as a "hermit."

"The military was not what Micah thought it would be," Delphine told The Blaze. "He was very disappointed, very disappointed. But it may be that the ideal that he thought of our government, what he thought the military represented, it just didn't live up to his expectations."

Johnson's Army Reserves engineering unit didn't see combat in Afghanistan, and some have speculated that this contributed to Johnson's shame. But his exit from the army resulted from a sexual harassment complaint filed against Johnson by a female corporal - which accused him of stealing women's underwear and recommended he receive mental health treatment.

He was sent home early from Aghanistan. The sexual harassment charges were eventually dropped, but Johnson was discharged from the military.

Johnson's 2014 return to the US coincided closely with the deaths of Eric Garner and Michael Brown, and the beginning of the Black Lives Matter movement. Johnson began to take a deep interest in black history, and he tried to join black power groups that urge armed resistance against white society, especially police.

But multiple black nationalist and black liberation groups wouldn't recruit Johnson because he was discharged from the Army due to sexual harassment.

"Once you're blacklisted by the alert that we put out, that's a wrap," Ken Moore of the Collective Black People's Movement told The Daily Beast.

Moore speculated that Johnson's rejection from several black power groups left him "ostracized" and led to a "psychological break."

Johnson remained loosely involved with the groups and attended events and protests in the area. On Facebook, he had liked The New Black Panther Party and the African American Defense League. And his account - which has since been deleted - featured photos of Johnson posing with a clenched fist, a symbol of the black power movement.

The Daily Beast has speculated that the letters Johnson wrote on a wall in his own blood the night of the shootings, "RB", were short for "RBG", or "red, black, and green" - the colors of the Pan-African flag and an acronym used by the Black Riders Liberation Party, which Johnson followed on Facebook.

Johnson's family told the Blaze he had never expressed anger towards white people. His stepmother, Donna, is white. But the deaths of Alton Sterling and Philando Castile seem to have pushed him over the edge.

According to Dallas Police Chief David Brown, Johnson had been planning a larger attack but expedited his plans in the wake of last week's police killings. Police found bomb-making materials, ballistic vests, rifles, ammunition, and a personal journal of combat tactics in Johnson's home.

Johnson told police after the shooting that he was seeking retribution for Sterling and Castile's deaths. But his father, James Johnson, told The Blaze that he couldn't understand his son's motives.

"I don't know what to say to anybody to make anything better. I didn't see it coming," he told The Blaze. "I love my son with all my heart. I hate what he did."