As Dallas came to grips on Monday with the aftermath of last week's sniper shooting targeting police, more details emerged about the gunman and his troubled past.
People took to the streets again in fresh protests over police shootings of black Americans, with hundreds of protesters blocking streets in America's third largest city Chicago.
The parents of gunman Micah Johnson, who killed five police officers during an ambush in Dallas on Thursday, said he was "disappointed" and grew reclusive after being discharged from the US Army in 2015.
"The military was not what Micah thought it would be," his mother Delphine told TheBlaze network.
"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 served six years as a private in the Army Reserve force and was in Afghanistan from November 2013 to July 2014.
His father James said it was after military service that Johnson began studying black history.
But relatives stressed that Johnson had never shown any signs of hatred for white people or other racial groups. His stepmother Donna is white.
"I didn't see it coming," said the 25-year-old's father, breaking down in tears.
Johnson opened fire at the Dallas demonstration that followed the deaths of two black men at the hands of police. In addition to killing five police officers, he also wounded nine others and two civilians. Johnson was killed by a bomb carried by a robot, in what experts have called a first. The city's police chief vigorously defended the tactic.
"This wasn't an ethical dilemma for me. I'd do it again," Dallas Police Chief David Brown said at a press conference.
"I would use any tool necessary to save our officers' lives. I'm not ashamed to say it."
The police chief told reporters that Johnson, who used a high-powered rifle, may have been planning a major bomb attack, with a "large stockpile" of bomb-making materials found at his home.
"He knew what he was doing. This wasn't some novice," Brown said. "We don't think he learned that in the military. We don't have any evidence of that."
Police investigators are combing through hundreds of hours of video evidence -- from officer body cameras, dash cams, and nearby businesses -- to try to piece together what happened.
"Detectives are reviewing over 300 statements to determine which witnesses and officers need to be brought back for further interviews," Brown added. Protesters spoke out against police shootings of black Americans.
Hundreds demonstrated in Chicago, clapping and banging drums, and shouting "No justice, no peace." Some passing cars honked in support.
In Atlanta, 16 protesters were arrested overnight outside the governor's mansion, CNN said, after the fifth consecutive night of demonstrations in the southern US city.
A smaller group protested in the California state capital of Sacramento.
Dallas Police Chief Brown, who said he and his family have received death threats, challenged those who have been protesting to consider working in law enforcement.
"We're hiring. Get off that protest line and put an application in," Brown said. "We'll put you in your neighborhood and we will help you resolve some of the problems you're protesting about."
In Dallas, civilians and police gathered for a moment of silence at a makeshift memorial in front of police headquarters.
Officers stood in a line, as others assembled in a circle around a police car covered with balloons and flowers.
The city planned a candlelight vigil Monday night at Dallas City Hall Plaza.
President Barack Obama and former president George W Bush plan to speak at an interfaith memorial in Dallas on Tuesday. Obama is also expected to meet privately with the families of police officers who were killed or injured.
The city was also getting ready for the funerals for the slain officers.
Funerals for Senior Corporal Lorne Ahrens of the Dallas Police Department and Brent Thompson of the Dallas Area Rapid Transit police will take place on Wednesday.
Funeral services for Sergeant Michael Smith of the Dallas Police Department are planned for Thursday. Plans for the other officers killed were not yet clear.