The shooter, Micah Xavier Johnson, said he was upset over the Black Lives Matter movement and the police shootings and was out "to kill white people", Dallas Police Chief David Brown said.
The Texas resident served as an active reservist for six years from 2009 to 2015, holding the rank of Private First Class and specializing in carpentry and masonry.
A suspect in Dallas was killed by law enforcement with a robot-delivered bomb in a parking garage where he had exchanged fire with officers, the Associated Press said.
Officials have named a suspect as 25-year-old Micah Johnson, who died after a stand-off with police.
Police were still investigating possible additional suspects on Friday, although Johnson reportedly said that he was acting alone.
Inside his home in Mesquite, ATF and police investigators found bomb-making materials, rifles, ammunition, ballistic vets, as well as "a personal journal of combat tactics", DPD said Friday.
He spent more than four years in Iraq, working for United States contractor DynCorp International as a police liaison officer who supervised Americans training and mentoring the Iraqi police force, the LinkedIn profile says.
Towards the end of his tenure, Johnson was deployed to Afghanistan from November 2013 and returned in July 2014.
Pastor Jeff Hood, one of the organizers of the downtown Dallas protest where five police officers were shot and killed, said he had never heard of Johnson.
As we reported, police said earlier that they took three other suspects into custody.
"It is a heartbreaking moment for the city of Dallas", Dallas Mayor Mike Rawlings said.
An undated handout image released by the Dallas Area Rapid Transit (DART) Police shows DART police officer Brent Thompson at an undisclosed location. "We stand with them in Newark, as well as anybody who has been killed in the last few days in violence that I think has been senseless".
"The discussion was simply to help curb this violence we've been seeing constantly whether law enforcement is involved or not", Hawkins said. "One of the things it can do is put our police officers in harm's way, and we have to be very careful about doing that".
Williams said her sister was shot in the right calf and had thrown herself over her four sons, ages 12 to 17, when the shooting began.
Barack Obama described the shootings as calculated and despicable.