(CNN)The ambush began with gunshots that killed five officers and sent screaming crowds scrambling for cover. It ended when a Dallas police bomb squad robot killed a gunman after negotiations failed.
Investigators have identified the dead suspect: 25-year-old Micah Xavier Johnson of Mesquite, Texas. But they're still trying to answer key questions. Chief among them: Was anyone else involved in the shootings, which began Thursday night during a protest against police violence and left parts of downtown Dallas under siege for hours? And are other suspects on the loose?
The deadly gunfire erupted in Dallas as videos showing two African-American men shot by police in Louisiana and Minnesota spurred protests and debate over police use of force across the country.
Officers shot during Dallas protest
Photos: Officers shot during Dallas protest
Five police officers were killed and seven others were injured in the ambush. It was the deadliest single incident for U.S. law enforcement since September 11, 2001. Two civilians also were injured in the shootings, the Dallas mayor's office said.
As officials condemned the attack Friday, details emerged about the suspect who died after a lengthy standoff with police in a parking garage.
The suspect told police negotiators that he was upset about recent police shootings, that he wanted to kill white people -- especially white officers -- and that he acted alone, the city's police chief told reporters Friday.
"We saw no other option but to use our bomb robot and place a device on its extension for it to detonate where the suspect was," Chief David Brown said. "Other options would have exposed our officers to grave danger. The suspect is deceased as a result of detonating the bomb."
Law enforcement sources familiar with the investigation told CNN that Johnson was the dead gunman. He had no criminal record or known terror ties, a law enforcement official said.
He had served in the U.S. Army Reserve, training as a carpentry and masonry specialist, two U.S. defense officials said.
Wayne Bynoe, a neighbor, said police cars were outside Johnson's home Friday. Johnson lived with his mother and "keeps to himself," Bynoe said.
The Dallas police chief told reporters it's too soon to speculate on the suspect's motives, and it's unclear whether more suspects are on the loose.
"We're hurting. Our profession is hurting. There are no words to describe the atrocity that happened in our city," he said. "All I know is that this must stop -- this divisiveness between our police and our citizens."
U.S. Attorney General Loretta Lynch described the Dallas shootings as the latest in a series of tragedies that have left the country reeling.
"After the events of this week, Americans across the county are feeling a sense of helplessness, of uncertainty and of fear. Now, these feelings are understandable and they are justified," she said, "but the answer must not be violence."
The attack
Witnesses said protesters were marching peacefully in downtown Dallas when the gunfire started Thursday night.
The Rev. Jeff Hood, one of the protest organizers, said he saw two officers go down, then watched a sergeant running toward the gunfire.
"I ran the opposite direction. I was concerned about the 700 or 800 people behind me," he said. "I was screaming, 'Run! Run! Active shooter! Run!' And I was trying to get folks out as fast as I could."
Crowds ran into a parking garage, witnesses said, and spilled out after word spread a sniper was nearby.
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Who are the slain officers?
"Everyone was screaming, people were running," said witness Clarissa Myles. "I saw at least probably 30 shots go off."
Police have said at least two snipers fired "ambush-style" from an "elevated position." Then police exchanged gunfire and negotiated with a suspect for hours at a parking garage in downtown Dallas.
Before authorities killed him with an explosive, the suspect told negotiators more officers were going to get hurt, and that bombs had been planted all over downtown.
Police found no explosives during sweeps of the area, Dallas police Maj. Max Geron said Friday morning on Twitter.
The victims
Police have said at least 10 officers were shot by a sniper, and that one officer was shot in a shootout at the parking garage. It's not clear where the 12th officer was shot.
Most of the injured officers have been released from the hospital, Brown told reporters. Their conditions are improving, Brown said, calling for the community to support them.
"We don't feel much support most days. Let's not make today most days," Brown said. "Please, we need your support to be able to protect you from men like these, who carried out this tragic, tragic event."
Dallas police Officer Patrick Zamarripa, a father of two, was one of the slain officers, according to social media posts from family members and reports from local media outlets. Military records show he was a U.S. Navy veteran who had been deployed to Bahrain as part of the Iraq War effort.
His brother shared a photo on Twitter with the caption: "Love you brother. Couldn't be prouder. We'll see you again. #PrayForDallas."
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Dustin @Dustin_Mfwood
Love you brother. Couldn't be prouder. We'll see you again. #PrayForDallas
2:02 AM - 8 Jul 2016
2,308 2,308 Retweets 3,653 3,653 likes
Dallas Area Rapid Transit Agency officer Brent Thompson was also killed.
Thompson, 43, joined the transit agency in 2009, and was its first officer killed in the line of duty.
He was a highly respected officer, DART police Chief James Spiller told CNN. And just two weeks ago, he'd gotten married to a fellow officer on the force.
"He was in great spirits," Spiller said.
The suspects
Brown said an investigation into the ambush continues. "Through our investigation of some of the suspects, it's revealed to us that this was a well-planned, well-thought out, evil tragedy by these suspects," he said Friday at a prayer vigil for the victims. "And we won't rest until we bring everyone involved to justice."
He would not say how authorities believe others in custody are connected to the shooting.
Previously, authorities had said three people were in custody, and that multiple shooters were involved in the attack.
"I'm not going to be satisfied until we've turned over every stone. We've got some level that this one suspect did do some of the shooting. But we're not satisfied that we've exhausted every lead," he said. "So if there's someone out there who's associated with this, we will find you, we will prosecute you, and we will bring you to justice."
Asked about the gunman's motive, Brown declined to speculate.
"We can't get into the head of a person that would do something like this. We negotiated with this person that seemed lucid during the negotiation. He wanted to kill officers, and he expressed killing white people, he expressed killing white officers, he expressed anger for Black Lives Matter. None of that makes sense," Brown said. "None of that is a reason, a legitimate reason, to do harm to anyone. So the rest of it would just be speculating on what his motivations were. We just know what he said."
The protests
The shootings occurred as many Americans nationwide took to the streets to demand answers over the killings of two black men in two days. They wept, marched and chanted, "Black Lives Matter!"
In St. Paul, Minnesota, crowds gathered near the spot where an officer killed Philando Castile in a car on Wednesday.
Previous
Gracen Daniel
@gracendaniel
Take away the racism. the hatred. the intolerance. the divide. the retaliation. the chaos. Give us Jesus. Please, give us Him. #Dallas
14h
Pharahstation86
@airstation86
No. Don't take a moment to pray, praying WILL NOT accomplish anything, this insanity needs to stop.
#Dallas
14h
Glynda Linkous
@GlyndaLinkous
Praying for all those affected by the shootings in Dallas last night. #DallasPoliceShooting #Dallas
9h
low energy jeb
@luis_camacho_0
The whole world is just looking at the United States in disbelief asking the same question: "Why do you let everyone have guns?" #Dallas
11h
Oge
@OgeTheYogi
To those who committed the killings of #Dallas policemen you are NO ally to the cause of peace and justice. This is NOT part of the solution
9h
Randy Mac
@RandyNBCLA
#Dallas whether you are a civilian or an officer you bleed the same. #stopthebleeding healing begins recognizing our humanity.
11h
Patrick McHugh
@Patattacks15
Sterling didn't deserve to die,Castile didn't deserve to die, those officers didn't deserve to die.I'm tired of all this violence #Dallas
11h
Mayor Buddy Dyer
@orlandomayor
We are stronger when we stand together both as a community and country. #WeStandWithDallas and all cities experiencing such difficult times.
9h
Rashida Jones
@iamrashidajones
My heart hurts. Too much death. Too much hate. Hug your loved ones tight. Tell them that in the darkest times, we MUST love even harder.
10h
Reverend Al Sharpton
@TheRevAl
We wake up to the horrific news from Dallas. The killing of police is wrong and reprehensible. We must be against all killings period!
10h
Dallas Police Depart
@DallasPD
It has been a devastating night. We are sad to report a fifth officer has died.
12h
Ted Cruz
@tedcruz
Men & women of law enforcement selflessly run into harm's way to save the lives of others. May God protect them and bring peace upon Dallas.
15h
ERENE
@Erene
How many moments of silence do we have to have until we aren't silent anymore? #Dallas
Topic: 5 white police officers killed in Dallas TX by black man (Read 2352 times)