Police Friday raided a home in the Dallas suburb of Mesquite, Texas, where the slain suspect in a shooting attack that killed five police officers lived, police said.
Police identified the man as Micah Xavier Johnson, 25, a black military veteran whom they believed carried out the sniper ambush in Dallas Thursday night on police guarding a protest against police violence. Fourteen people were shot, including two civilians.
Johnson told negotiators he was the only shooter, police said. Investigators now believe he acted alone, after earlier reports by police and witnesses in the chaotic hours following the attack had described a coordinated attack by several shooters.
Dallas Mayor Mike Rawlings said there had been confusion about the number of shooters because the gunman was moving during the attack.
US President Barack Obama was cutting short a trip to Europe to return home on Sunday to deal with the attack, scaling back his planned activities in Spain to return a day earlier than planned before traveling to Dallas next week.
"The president will continue the work to bring people together to support our police officers and communities, and find common ground by discussing policy ideas for addressing the persistent racial disparities in our criminal justice system," spokesman Josh Earnest said.
Police said they had arrested another 25-year-old man at the scene on what they described as "unrelated" weapons charges. Police had earlier said three people were in police custody, including one Rawlings earlier identified as a black woman.
Texas Governor Greg Abbott said authorities were working to identify any potential conspirators.
The US military confirmed that Johnson had served in the US Army reserve until last year, and had been deployed to Afghanistan from November 2013 to July 2014.
Police said a search of Johnson's home turned up bomb making materials, ballistic vests, rifles, ammunition, and a personal journal of combat tactics.
The attack just before 9 pm Thursday (0200 GMT Friday) began as officers were mowed down by sniper fire as the peaceful demonstration ended. A street-level shootout ensued, and police exchanged gunfire for hours with Johnson, holed up in a parking garage near the city's El Centro College.
Police said they killed him with a bomb carried by a robot into the garage - possibly the first time a robot has been used to kill a suspect, according to news reports.
The White House ruled out any connection to terrorism in the attack. In Warsaw for a NATO summit, Obama condemned the shootings as "vicious, calculated and despicable" and said "justice will be done."
Obama ordered flags lowered to half-mast in mourning.
But even as the violence united the country in condemnation, it once again laid bare ongoing tensions between law enforcement and the black community over violence and allegations of bias.
The slain police officers were guarding a demonstration by activist group Black Lives Matter protesting the killing of two black men by police elsewhere in the country earlier in the week.
Alton Sterling, 37, was shot and killed in Baton Rouge Tuesday and Philando Castile, 32, in suburban Minneapolis Wednesday. Castile's girlfriend live-streamed video as he died from four gunshot wounds, shot as he reached for his wallet to show a police officer who had pulled him over for a broken tail light.
Police said the Dallas shooter told negotiators he was angry about the deaths at police hands and about Black Lives Matter and wanted to kill white police officers.
"Racial issues continue to divide us. Yes, it's that word race and we have to attack it head on," Dallas Mayor Mike Rawlings said at an outdoor prayer service attended by hundreds of mourners in Dallas' Thanksgiving Square Friday.
"All I know is this must stop. This divisiveness between our police and our citizens," Dallas police chief David Brown said earlier in the day.
But in a sign of persistent divisions, Lieutenant Governor Dan Patrick lashed out at Black Lives Matter protesters, blaming their movement for violence against police and calling them "hypocrites" for seeking police protection from gunfire, according to the Dallas Morning News.
The attacks renewed calls by Obama and Democratic leaders for legislative action on gun control, which the Republican congressional majority have refused to allow.
"When people are armed with powerful weapons, unfortunately, it makes attacks like these more deadly and more tragic. In the days ahead, we are going to have to confront those realities as well," Obama said.
Democratic Representative GK Butterfield, chair of the Congressional Black Caucus, told media that without legislative action, the country's entrenched conflicts on race and guns could turn combustible again.
"If we fail to act, this will be a long, hot summer," he said.