Peaceful protest turns chaotic as sniper shoots Dallas police

Last Updated Jul 8, 2016 4:58 PM EDT

Police officers were ambushed by sniper fire in downtown Dallas Thursday night, as a peaceful protest turned into chaos.

Five officers were killed. Seven other officers and two civilians were wounded.

Police said the attack was a mission to kill as many officers as possible. A suspect, later identified as 25-year-old Micah Xavier Johnson was killed after a standoff with police. Police Chief David Brown said negotiations broke down and authorities "saw no other option" but to to use a bomb robot to carry an explosive over to the suspect's location and detonate it.

"Other options would have exposed our officers to grave danger. The suspect is deceased as a result of detonating the bomb," Brown said during a press conference Friday morning.

During the negotiations, however, Brown said the suspect told them he was upset over the recent police shootings of black victims and wanted to kill white people, especially white police officers. Earlier, police had said three other suspects were in custody, but

Video: Shots ring out in Dallas

The evening began with a protest march in solidarity with victims in this week's police killings of two men in Louisiana and Minnesota, reports CBS News correspondent Manny Bojorquez. But just before 9 o'clock, officers with the Dallas Police Department and Dallas Area Rapid Transit (DART) were targeted by an enemy they couldn't see.

The unprecedented assault unleashed dozens of rounds on downtown Dallas. People marching at the rally stopped walking to run for their lives.

The view from above shows how hundreds of people scattered.

"I was screaming, 'Run, run, run! Active shooter, active shooter!"' the Rev. Dr. Jeff Hood, a rally organizer, said.

Mistaken Dallas shooting "suspect" describes ordeal

As the attack went on, several uniformed officers were down, motionless, on the pavement outside. Officers ran to the aid of their wounded colleagues even as the gunfire continued.

One of the suspects, a man with a rifle, fired shots while hiding behind a pillar.

"We got a guy with a long rifle but we don't know where the hell he's at," an officer could be heard saying over the police scanner.

Sister: Women caught in Dallas crossfire shielded son from gunfire

Two suspects were arrested in a traffic stop after a brief chase. Police also detained a woman in a community college parking garage.

Four of the officers who were killed were with the Dallas Police Department. One was a DART officer.

"It is a heartbreaking morning. ... To say that these police officers put their lives on the line every day is no hyperbole, it's a reality," Dallas Mayor Mike Rawlings said.

The shooter who was involved in the standoff with police claimed bombs were planted throughout the area. Dallas police, joined by ATF personnel, used bomb sniffing dogs to search the downtown area, and found no explosives, a law enforcement source told CBS News senior investigative producer Pat Milton.

Police on alert nationwide after Dallas ambush

Police officials CBS News spoke to around the country described an unease for the safety of police on patrol, reports CBS News correspondent Kris Van Cleave.

The New York Police Department has increased security around all city precincts. Washington D.C.'s metropolitan police briefed officers on the shootings at roll call Friday morning and now has all officers working in pairs. Miami police told us they will be gathering Friday to create contingency plans for their city, while the Las Vegas Police Department said its officers will be working in pairs until further notice.

This is not the first time in recent memory that officers have come under fire during a protest. In Ferguson, Missouri in March of last year, two cops were shot during a demonstration outside of police headquarters.

A former law enforcement source told CBS News adding additional cops to patrols is common in situations like this. But despite heightened concern for their safety, it is also in the back of officers' minds to be extra careful with their actions because they themselves are more in the spotlight than ever.