President Obama will pay tribute Tuesday afternoon to the five police officers killed in last week's ambush in Dallas. He will attend and speak at a private, interfaith memorial service, and former President George W. Bush will also deliver remarks. Both will meet with victims' families.
Michael Smith, Lorne Ahrens, Michael Krol, Brent Thompson and Patrick Zamarripa were all remembered in a vigil Monday night, as more than 1,000 people gathered at Dallas city hall for the candlelight service.
While crews and security are preparing for the service, authorities are combing through more than 170 hours of videotape and reviewing more than 300 statements in an effort to piece together last week's attack, reports CBS News correspondent Manny Bojorquez.
Dallas Police Chief David Brown said investigators are questioning gunman Micah Johnson's mother, Delphine Johnson, who shared her Dallas-area home with her son.
"We're going to follow every lead until it's exhausted, until I'm satisfied that this was the lone person," Brown said.
A search of the house revealed bomb-making materials, including metal pipes of different lengths, chemicals, rifles and body armor, according to a source.
In an interview with The Blaze, Delphine said she watched her son transform from a fun-loving extrovert into a "hermit" when he returned home from Afghanistan accused of sexual harassment.
"He was very disappointed," she said.
Johnson was discharged from the Army in 2015 following the allegations.
"It may be that the ideal that he thought of our government of what he thought the military represented -- it just didn't live up to his expectation," Delphine said.
"I don't know what to say to anybody to make anything better," Johnson's father, James Johnson, said with tears streaming down his face.
James said he never could have foreseen his son's deadly rampage.
"I love my son with all my heart. I hate what he did," he said.
A law enforcement source tells CBS News Johnson had hundreds of rounds of ammunition attached to his body when he carried out the attack, an indication he meant to kill more people. Thirteen officers used force in the standoff, 11 fired their weapons and two used a robot to detonate a bombto kill Johnson -- a decision Chief Brown has since defended.
"This wasn't an ethical dilemma for me. I'd do it again," Brown said.
When asked what young black men can do to overcome their fear of cops, Brown said, "We're hiring."
"Get off that protest line and put an application in. ... We will help you resolve some of the problems you're protesting about," he added.
The FBI is still investigating the cryptic letters "R.B." written by Johnson in his own blood in two locations before he died.
Brown said he and his family have received death threats following Thursday's shooting. He said he's considering mandating counseling for officers, so that anyone who may need help following the shooting won't have to ask for it.