In a statement released on Friday, the army said Micah Xavier Johnson served with US forces from March 2009 to April 2015 and was a carpentry and masonry specialist with the 420th Engineering Brigade based in Texas. He achieved the rank of private first class on May 2010 before being sent to Afghanistan for eight months in November 2013.

Johnson allegedly opened fire on police during a protest in Dallas, Texas, on Thursday night, killing four police officers and a transit officer during a protest rally against police brutality. Seven police officers and two civilians were also wounded in the attack.

Following several hours of shooting and negotiations, police used a robot bomb to kill Johnson after he barricaded himself in a downtown garage. According to authorities, the bomb was used to avoid endangering officers' lives.

Holed up in the garage, Johnson had reportedly told police that there were bombs strewn throughout the garage and other places in downtown. Bomb squads later swept the area and did not find any explosives.

Nationwide protests

The attack on Thursday came amid protests across the US against police brutality after two videos emerged this week of police killing two black men in the states of Minnesota and Louisiana.

Philando Castile, 32, was shot during a traffic stop near Minneapolis, Minnesota, on Wednesday. Minnesota Governor Mark Dayton reignited a national debate after saying that police probably would not have fired if Castile had been white.

One day earlier, police gunned down 37-year-old Alton Sterling outside a shop in Baton Rouge, Louisiana.

Gunman wanted to target white officers

Dallas Police Department (DPD) Chief David Brown said on Friday that prior to his death, Johnson told negotiators he was upset over police killings of black people and wanted to kill white people, "especially white officers."

Police were still investigating possible additional suspects on Friday, although Johnson reportedly said that he was acting alone.

One man who was seen carrying an assault rifle during the Dallas protest was released shortly after being taken in for questioning. The man told local media that he was mistakenly identified as a suspect, adding that he was legally carrying a firearm. Texas is an open-carry state, which allows individuals to carry certain guns as long as they are visible.

'No possible justification'

Speaking from a NATO summit in Poland on Friday, US President Barack Obama said he had been informed about the situation in Dallas and that the federal government would provide assistance to local authorities.

"There is no possible justification for these kinds of attacks or any kind of violence against law enforcement … Justice will be done," Obama said.

"When people are armed with powerful weapons, it makes attacks like this more deadly," he added.

At an outdoor prayer service attended by hundreds of mourners in Dallas on Friday, the city's mayor, Mike Rawlings, said: "Racial issues continue to divide us."

"Yes, it's that word race and we have to attack it head on," he said, adding that it was time to be honest about the "shortcomings" of his generation in dealing with racial injustice.

"This is on our watch," he said.

ksb/kms (AFP, AP)