The protesters were angry, but they were peaceful. Even the uniformed police officers walking and taking pictures with them — symbols of the system they were denouncing — remarked how smoothly the Thursday evening march through downtown Dallas was going.
But nearby, someone far angrier was about to take aim.
The marchers were about 800 strong — blacks and whites, adults and children, veteran activists and regular citizens — venting their frustration with the recent killings of black men by cops in Louisiana and Minnesota. They streamed through the sticky heat with chants of "Enough is enough" and "Hands up, don't shoot."
At the front of the procession, near the intersection of Commerce Street and Austin Street, organizer Jeff Hood carried a 10-foot cross and chatted with a sergeant. The rally was winding down. It was 8:58 p.m.
"All of a sudden: pow-pow. Pow-pow-pow-pow. Pow-pow," Hood recalled. He looked up and saw what he believed was two officers drop. He felt his body to make sure he hadn't been hit. He called out to anyone who could hear: "Run, run!" Holding his cross high, he tried to lead the way.
"We were all wondering how something so beautiful could turn so evil so quickly," Hood said later.
The scene lurched into pandemonium, marchers screaming and scrambling for cover, grabbing kids.
"It was chaotic. People were trying to find shelter. No one knows who's shooting, or where the shots are coming from," the Rev. Michael Waters said. "Individuals were with me gathered behind a pillar. And as individuals continued to run in our direction, I felt unsafe and began to move individuals with me to another location where we could get out of the way of the gunfire."
The shooting continued in bursts, echoing off the downtown high-rises. To Carlos Harris, the rhythm of the gunfire made it sound strategic. "It was tap, tap, pause. Tap, tap pause," he told the Dallas Morning News.
It was clear to anyone there who was being targeted. "I didn't see anybody else get shot, just the cops. I saw cops getting shot, right there in plain sight," Cortney Washington told NBC Dallas-Fort Worth.
But others got hit. Shetamia Taylor, who'd brought her four sons to the march, was shot in her right calf, and immediately threw herself over one of her boys, her sister said. The other three darted for cover.
Officers ran to their fallen colleagues. Others pulled their guns and searched for the source of the gunfire. More patrol cars rushed to the scene, sirens blaring. The air began to reek of gunpowder.
In the chaos it was impossible to tell how many people were firing on them. Officers began ordering suspicious looking people down on the ground, but it was unclear that they were involved.
"Shots fired. Officer down. Assist officer," one barked over the police radio.
Gunfire cracked in the background. An officer called out, "Get over here."
A bit later: "Yo, we got a guy with a long rifle, but we don't where the hell he's at."
Witnesses spotted him, dressed in what appeared to be khaki military gear near the entrance of a building at El Centro College on Lamar Street. One man told a local television station that he'd watched as the gunman pulled on a tactical vest and opened fire on a passing police car.
In a confrontation captured by a witness' video camera from above, a police officer rushed at the gunman, shooting while taking cover from behind a pillar. The gunman turned on the officer and shot him down.
People kept scattering, not sure where to go. Parents lost track of their children, wives of their husbands.
"The most terrifying part was us being separated and not knowing where the bullets were coming from and seeing an officer just drop in front of you," said Earnest Walker III, a pastor who'd brought his college-age son, also named Earnest, to the march.
"They were there to support us," Walker said.
"They were helping us," his son said.
The young man added, "This was supposed to be a good thing. Everyone was working together."
At some point, the gunman, later identified by a senior law enforcement official as 25-year-old Army veteran Micah Xavier Johnson, entered an El Centro College parking garage, where police cornered him. Over the next few hours, officers spoke with him. He told them he was upset about the Black Lives Matter movement, and about this week's police shootings of black men in Louisiana and Minnesota, and about white people. "The suspect stated he wanted to kill white people, especially white officers," Dallas Police Chief David Brown said.
The gunman also told officers he wasn't connected to any groups and was acting alone, Brown said. He warned that he'd placed bombs nearby.
Finally, in Friday's early morning hours, negotiations broke down, and a shootout erupted, police said. Police sent in a bomb robot, armed with explosives, aimed it at the gunman and detonated it. Johnson was killed.
Senior U.S. law enforcement officials told NBC News that the investigation has led them to believe that Johnson was the lone gunman, although that conclusion could change. And authorities are still trying to determine if any others helped him. Three people were taken into custody prior to his death, police said, but they had not been identified as suspects.
The gunfire's final toll: 12 police officers shot, five fatally, and two civilians injured.
The long night ended at Baylor Medical Center, were some of the injured were taken. In the predawn quiet, officers waiting outside snapped to attention. They saluted as two bodies were carried outside and placed into a medical examiner's van. A police escort arrived, and led the van away.