A day after at least five police officers were shot and many injured on Thursday night after a shooter opened fire during a protest in Dallas over the recent fatal police shootings of black men in the US, more details of the shooter have emerged.

The gunfire broke out late Thursday during an otherwise peaceful protest over the deaths of Philando Castile in Minnesota and Alton Sterling in Louisiana.

BBC reported:

Micah Xavier Johnson, who was himself killed by police, was a US army veteran who had served in Afghanistan. The 25-year-old was a private who did a nine-month tour of duty from November 2013 after serving in the Army Reserve for six years. Johnson acted alone and had no known criminal history or ties to terror groups. He lived with his mother in the quiet Dallas suburb of Mesquite.

The Associated Press reported that the Dallas police found bomb-making materials, ballistics vests, rifles, ammunition and a journal full of combat tactics during a search of his residence.

Speaking to The Telegraph, Johnson's friend said "He was upset. He said white cops are just slaying black people, basically genocide. He said, "this is getting out of hand'.He loved basketball, he was good. I saw him a week ago. He was a pretty cool dude, chilled. He just didn't seem the type to do this. I never saw him angry."

"This was a vicious, calculated and despicable attack," Obama said of the Dallas shootings at a press conference during the North Atlantic Treaty Organization Summit in Warsaw.

Obama vowed that anyone involved in the senseless murders would be held fully accountable.

"When people say 'black lives matter', it doesn't mean that blue lives don't matter," Obama said.

He also said data showed black citizens were more vulnerable to acts of violence than their white neighbours.

"There is no possible justification for these kinds of attacks or any violence against law enforcement," he said, emphasising that "justice will be done".