Police said they found bomb-making materials as well as more guns and ammunition in Johnson's home in a Dallas suburb. The aftermath of the shooting was purportedly livestreamed in a widely shared Facebook video.
The Dallas shootings have amplified fears around safety, both for members of law enforcement and their families, as well as protesters pushing for reform within police departments around the country.
"(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. One was Brent Thompson, 43, who joined the Dallas Area Rapid Transit police department in 2009, according to police.
"It's a [Dallas Police Department]-led criminal investigation", said Allison Mahan, a spokeswoman for the FBI's Dallas office, when asked if the incident was being investigated as domestic terrorism.
"Any death, it doesn't matter whether it's a police officer or this man's father, all lives matter", she said.
A Tennessee man accused of shooting indiscriminately at passing cars and police on a highway told investigators he was angry about police violence against African-Americans, authorities said.
"We deal with all kinds of people down here, so we try to have someone with the personality to deal with all kinds of individuals, someone with a personal touch and not a heavy-handed approach", Spiller said.
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. The attack followed last week's two shootings of black males by police officers. "He is confused. I don't let my children use profanity around me, but he was using cursing and I said, 'O.K., he is really upset.' I need to get a hold of this young man and explain to him that he is seeing things that we have shielded him from his whole life".
Zamparripa was a 32-year-old, Navy veteran who served three tours in Iraq.
Thousands of people marched in Atlanta, Georgia to protest the shootings of black citizens by white police officers in Minnesota and Louisiana.
All five of the police officers shot dead have been named. Other people later joined the officers for an impromptu vigil.
She said she was still at work as news of the Dallas killings trickled in, with the death toll rising to five.
Mark Hughes was identified as a suspect shortly after the attack. He has since been released from custody.
There was no sign of global links to the attacks, U.S. officials said on Friday.
The violence broke out as hundreds of people gathered in Dallas to protest this week's fatal police shootings in Baton Rouge, Louisiana, and suburban St. Paul, Minnesota.