The slain suspect in an ambush that killed five Dallas police officers last week had plans for larger attacks, the city's police chief said Sunday.
The man also left a cryptic message in blood on a wall before police killed him in a targeted explosion, Dallas Chief of Police David Brown told CNN.
"We're convinced that this suspect had other plans and thought that what he was doing was righteous and believed that he was going to target law enforcement — make us pay for what he sees as law enforcement's efforts to punish people of color," Brown said.
WATCH: President Barack Obama comments on incident
Police believe Micah Xavier Johnson, 25, is the lone shooter in the deadly attack Thursday night during a protest against police killings of African-American men. The Dallas police chief said Friday that during hours of negotiations with Johnson, the gunman told police he wanted to "kill white people, especially white officers."
Before he was killed by police, Johnson also told negotiators he acted alone and was unaffiliated with any group. Brown said investigators have not definitively ruled out that Johnson had accomplices.
The police chief also revealed to CNN that police found the letters "RB" written in blood on a wall in the parking garage where Johnson was killed by police after he refused to surrender.
The meaning behind the message remains unclear, he said.
Seven other officers and two civilians were also wounded in the shooting; but new information released by Brown indicates the violence could have been even worse.
Bomb-making materials
Bomb-making materials and a journal were found at Johnson's home during a search Friday.
"The material were such that it was large enough to have devastating effects throughout our city and our North Texas area," Brown told CNN.
He added that the shooter "obviously had some delusion. There was quite a bit of rambling in the journal that's hard to decipher."
Johnson, an African-American man from the Dallas suburb of Mesquite, was a U.S. Army Reserve veteran who served in Afghanistan, according to U.S. defense officials.
Though trained in carpentry and construction through the military, NBC News reports that Johnson was most recently working for a company that provides care for people with disabilities. The owner of Touch of Kindness, a community social services organization based in Dallas, told NBC Johnson was paid an hourly wage to care for his brother at the family's home.
A woman who answered the phone at the company said she was shocked that Johnson was connected to the attack.
"He's not that kind of person," she said. "He's not violent. That can't be him."
The lead instructor at a private self-defense school near Dallas confirmed to the Associated Press that Johnson trained at the Academy of Combative Warrior Arts about two years ago; the school teaches special tactics, including how to change positions in between firing off a gun.
In Pictures: A Nation Protesting and Mourning
A Nation Protesting and Mourning
Nationalist groups
Although officials have not established any links to political groups, media reports suggest Johnson expressed sympathies on social media to several black nationalist organizations, including the New Black Panther Party.
Krystal Muhammad, national chair of the New Black Panther Party, told VOA that she didn't know Johnson and had never heard of him before the Dallas attack.
"I don't know where they're getting that information," Muhammad said. "People say a lot of stuff but that doesn't mean it's accurate."
When asked her opinion on the attack, Muhammad said: "My moral judgement is an eye for an eye and a tooth for a tooth."
"What happened in Dallas, who knows, this could be happening all across America. Because people are fed up. You cannot continue to brutalize human beings and think that some human beings are going to fall for it," she said.
The New Black Panther Party is a black political organization founded in Dallas. It is named after, but not an official successor to the now defunct Black Panther Party, the black nationalist group that frequently clashed with police in the 1970s.
Other than Johnson's social media activity, there was no indication that he had any ties to the Panthers or any other group.
An obscure organization, called Black Political Power Organization, appeared to claim responsibility for the attack on Facebook, but the page was later deleted, and no other information about the group, if it even exists, was readily available.
U.S. law enforcement officials say Johnson did not have a criminal record.
Army record
In an emailed statement, the U.S. Army said Johnson was a carpentry and masonry specialist during his time in the service from March 2009 to April 2015. He was deployed to Afghanistan from November 2013 to July 2014.
Johnson received several low-level military awards during his time in the Army, according to the statement, including the Global War on Terrorism Service Medal, which is given to service members who have served in support operations in support of the U.S.' Global War on Terror (GWOT).
Johnson left Afghanistan when a fellow soldier brought sexual harassment charges against him saying he needed mental health counseling.
VOA's Jeff Seldin contributed to this report updated July 10, 2016.
