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The gunman killed in a stand-off with Dallas police said he wanted to kill white people, especially officers, the city's police chief has said.
The suspect, named by US media as Micah Johnson, 25, said he was upset about the recent police shootings of black people, Police Chief David Brown said.
Five Dallas police officers were killed and seven wounded by snipers during a march against the shooting of black men by police, officials say.
Three people are in custody.
Mr Brown said the suspect had been killed when police used explosives placed by a robot to end a tense stand-off in a building where he was holed up. Before that he had spoken to a negotiator.
"He said he was upset about Black Lives Matter [protest movement]; he said he was upset about the recent police shootings," Mr Brown told a news conference.
"The suspect said he was upset at white people. The suspect stated that he wanted to kill white people, especially white officers."
At the scene - Tara McKelvey, BBC News, Dallas
Red roses and worn-looking stuffed toys are left on Griffin Street near the place where the officers were shot.
Dozens of police are now patrolling the area under a harsh afternoon sun, and workers from a nearby Westin hotel are lugging around bottled water and granola bars to give to the officers.
Things are tense. Brandt Sadlowski, 24, got into an argument with the officers over his handgun, a 9mm that he carries on his belt.
That's legal in Texas, but the officers asked him to steer clear of the memorial site. The police don't want any more incidents - especially not today.
Mr Brown added that the man had said he was not affiliated with any groups and he acted alone. However, police had previously said they believed that more than one gunman was involved.
Micah Johnson was from Mesquite, an eastern suburb of Dallas, and was a member of the US Army Reserve, US media reported.
Gunfire broke out at around 20:45 local time on Thursday (01:45 GMT Friday) as demonstrators marched through the city. There was panic as people scrambled for cover. Police described the ambush as carefully planned and executed.
The protests came after this week's deaths of Philando Castile in Minnesota and Alton Sterling in Louisiana.
The mother of one of Alton Sterling's five children denounced the Dallas killings, saying in a statement through her lawyer that "responding to violence with violence is not the answer".
"Our hearts break for the families of the officers," Quinyetta McMillon said.
President Barack Obama, who is attending a Nato summit in Poland, called it a "vicious, calculated and despicable attack on law enforcement".
US Attorney General Loretta Lynch described events in Dallas as "an unfathomable tragedy".
"Americans across our country are feeling a sense of helplessness, of uncertainty and of fear," she said.
"These feelings are understandable and they are justified. But the answer must not be violence."
Speaking earlier on Friday, Mr Brown said two snipers had fired from "elevated positions", shooting some officers in the back
"We believe that these suspects were positioning themselves in a way to triangulate on these officers from two different perches... and planned to injure and kill as many law enforcement officers as they could," he said.
The Dallas attack marks the deadliest day for US law enforcement officers since the 9/11 attacks in 2001.
Officers later surrounded a car park near El Centro College where the stand-off with the suspect took place.
Dallas Mayor Mike Rawlings said that two civilians, one man and one woman, were also injured in the shootings.
He told the NBC Today programme that the suspects in custody so far were not co-operating and were "tight-lipped".
The Dallas protests were among several held across the US over the police use of lethal force against African Americans.
Philando Castile was shot dead after being stopped in his car by police in St Paul, Minnesota , on Wednesday.
Alton Sterling was killed by police a day earlier in Baton Rouge, Louisiana.
Both incidents were captured on video, reigniting what has become a national debate.
