The violent ambush that killed five Dallas police officers and wounded seven more could have been a lot worse, the city's police chief says.
Dallas Chief of Police David Brown told CNN Sunday that the slain gunman told police negotiators he wanted to "kill white people, especially white officers."
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 said.
Micah Xavier Johnson, 25, was killed by police in the deadly attack Thursday night during a protest against police killings of African American men.
Since the shooting deaths of two black men by white police officers over two days last week, protests have been held across the country. Scores of demonstrators have been arrested, with one flash point being the southern city of Baton Rouge, Louisiana, where DeRay McKesson, one of the most prominent activists linked to the police reform protest movement Black Lives Matter, live streamed his own arrest.
Police defended his arrest as a matter of public safety, but demonstrators told U.S. news outlets they believe McKesson was targeted.
McKesson was freed on bond Sunday afternoon after being charged with obstructing a highway. "I remain disappointed in the Baton Rouge police, who continue to provoke protesters for peacefully protesting. There's a lot of work to be done, with this police department specifically,'' he said.
But Louisiana Governor John Bel Edwards disagreed with McKesson's assessment. The governor told a news conference Sunday that he is proud of the state's law enforcement officers, calling their response to the protests "moderate."
In the northern city of St. Paul, Minnesota, where a second man, Philando Castile, was shot to death last week by a policeman after a traffic stop for a broken tail light, hundreds of protesters hurled firecrackers, rocks and bottles at police on Saturday.
The heavily armed officers used smoke grenades and pepper spray to break up the demonstration, with about 100 arrests. Authorities said 27 police officers were injured in the clashes.
Protests were held in other cities, too, including Washington, New York, San Francisco, Nashville and Indianapolis.
Individuals fired at police in at least two states -- Tennessee and Wisconsin -- and numerous police officials in major cities ordered their officers to patrol in pairs to give them a measure of safety.
In Pictures: A Nation Protesting and Mourning
President Barack Obama, who cut short a visit to Spain and will visit Dallas this week, said police and activists need to listen to each other. He said violence against police officers is a "reprehensible crime" that needs to be prosecuted.
"But even rhetorically, if we paint police in broad brush without recognizing that the vast majority of police officers are doing a really good job and are trying to protect people and do so fairly and without racial balance ... then we're going to lose allies in the reform cause," Obama said Sunday in Madrid.
The president will deliver remarks Tuesday at an interfaith memorial service in Dallas. The White House says he is making the trip at the invitation of Dallas Mayor Mike Rawlings.
Also Sunday, Brown defended his decision to end the hours-long standoff in Dallas, ordering the use of a robot equipped with a bomb that police detonated to kill Johnson after negotiations for his surrender failed.
WATCH: Dallas Honors Fallen Officers
Some law enforcement officials have questioned use of the robot to kill an active shooter, apparently a first in U.S. law enforcement, that some say draws a close parallel with the use of U.S. military drones to killed terrorists in the Middle East.
But Brown said the gunman was hiding behind a brick wall and that police assault teams would have been exposed to "the gravest danger" if they had tried to rush Johnson to end the mayhem.
The police chief told CNN, "I approved it and I'd do it again if presented with the same circumstances. (Johnson) seemed very much in control and determined to hurt more officers."
Brown dismissed critics "sitting in the comfort of their homes" about the use of the robot because "they're not on the ground" trying to end Johnson's assault on police.
Dallas Mayor Rawlings, speaking on CBS' Face the Nation, said he agreed with the decision. He stressed that Johnson was given an opportunity to surrender.
"We ask him, 'Do you want to come out safely or do you want to stay there and we're going to take you down?' And he chose the latter," Rawlings said.
At churches around Dallas Sunday, people offered prayers for the victims and their families.
"We need to come together and pray for our leaders. And we need to pray for God's healing on our nation," said Robert Jeffress, senior pastor at First Baptist Church in Dallas.
VOA's Mike O'Sullivan in Dallas contributed to this story.