**UPDATE 1: We learned just moments via ABC News that the suspect in Thursday nights deadly Dallas shooting did not die from a self-inflicted gun shot wound but rather by bomb detonation.
Dallas Police Chief: We cornered one suspect, tried negotiations for hours, there was gunfire, we saw no other option than to use bomb robot— ABC News (@abcnews) July 8, 2016
In a scene reminiscent of a warzone, eleven Dallas police officers were shot overnight by at least two snipers here Thursday night during a protest over police brutality, leaving five officers dead and wounding six, throwing the city into chaos and turning parts of downtown into a massive crime scene by Friday morning. Dallas Police Chief David Brown said the snipers had opened fire on officers from “elevated positions” during the protests. A civilian was also wounded. The attack was one of the worst mass shootings of police in U.S. history.
Police described Thursday night's ambush as carefully planned and executed and had taken three people, including a woman, into custody before a fourth died from what Dallas-based media said was a self-inflicted gunshot after a standoff that extended into Friday morning. A fourth suspect exchanged gunfire with police in a tense, hours-long standoff with police overnight, but that confrontation ended early Friday morning when he reportedly shot himself.
The suspect in the standoff had told police "the end is coming" and that more police were going to be hurt and killed. Brown said the suspect also told police "there are bombs all over the place in this garage and downtown".
BREAKING: Suspect holed up in Dallas parking garage reportedly dies from self-inflicted gun shot wound.— Fox News (@FoxNews) July 8, 2016
Police said they were questioning two occupants of a Mercedes they had pulled over after the vehicle sped off on a downtown street with a man who threw a camouflaged bag inside the back of the car. A woman was also taken into custody near the garage where the standoff was taking place.
"We are leaving every motive on the table on why this happened and how this happened," Brown said.
Police are working on the assumption that all four may have been involved in the attack. It appeared the suspects had knowledge of the protest route, allowing them to take up “triangulated” positions above the march and target officers. Police were still searching for other suspects over night, just hours before thousand of workers would fill offices, restaurants and shops in the downtown.
“We still don’t have a complete comfort level that we have all the suspects,” Chief Brown said, adding a search of the area was continuing. Police and city officials said that large areas of downtown would be closed Friday as police continued their investigation.
Dallas Mayor Mike Rawlings told Dallas residents to check with a city website and their employers to see if they would have access to their workplaces. Parts of the city are “an active crime scene,” Mayor Rawlings said, “and we are asking you to stay away from that area.”
Police didn't release the identities of the suspects, and said their motives were unclear. The suspects were being questioned by police, but were uncooperative, Chief Brown said.
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The violence started on Thursday night during a peaceful protest in Dallas over the fatal shootings of Alton Sterling in Baton Rouge, LA, and Philando Castile in St. Paul, MN. At least four attackers, holed up in a downtown garage, used sniper rifles against police officers. The incident then sprawled to the streets, where major corporations, restaurants and courthouses have premises. Police believe the attack was coordinated.
"[They were] working together with rifles, triangulating at elevated positions in different points in the downtown area where the march ended up going," Dallas Police Chief David Brown told a news conference.
Brown also said the suspects had threatened to plant bombs in the downtown Dallas area. Two officers of those injured in the shooting are in surgery while three remain in a critical condition, according to KTRK news. The condition of the sixth injured officer is unknown.
President Barack Obama, while in Poland, said he had spoken to Rawlings and expressed his "deepest condolences" on behalf of the American people. "I believe I speak for every single American when I say that we are horrified over these events and we are united with the people and police department in Dallas," he said.
Obama said the FBI was in contact with the Dallas Police Department and that the federal government would provide any assistance to Dallas as it deals with the incident.
"We still don't know all of the facts. What we do know is that there has been a vicious, calculated and despicable attack on law enforcement," he said.
No specific motive has been given for the shootings at the downtown protest, one of many held in major cities across the United States on Thursday. New York police made more than a dozen arrests on Thursday night, while protesters briefly shut down one of Chicago's main arteries.
Dallas Police Chief David Brown said the shooters, some in elevated positions, used sniper rifles to fire at the officers in what appeared to be a coordinated attack.
"(They were) working together with rifles, triangulating at elevated positions in different points in the downtown area where the march ended up going," Brown told a news conference, adding a civilian was also wounded.
"It has been a devastating night. We are sad to report a fifth officer has died," Dallas police said on Twitter.
Mayor Rawlings advised people to stay away on Friday morning as police combed the area where large areas have been cordoned off and transport halted. Federal authorities also halted commercial air traffic for the area as police helicopters hovered over the scene.
"Our worst nightmare has happened," he said. "It is a heartbreaking moment for the city of Dallas."
Police were conducting bomb sweeps throughout downtown Dallas, where officials said many county offices were to be closed on Friday.
The Dallas-Fort Worth metropolitan area is one of the nation's most populous and is home to more than 7 million people.
The use of force by police against African-Americans in cities from Ferguson, Missouri, to Baltimore and New York has sparked periodic and sometimes violent protests in the past two years and has spawned the Black Lives Matter movement.