The American flag flies at half staff as visitors explore Dealey Plaza in Dallas. President John F. Kennedy was assassinated in 1963 in this area, which is about two blocks from where a sniper killed five police officers last week. (Bonnie Jo Mount/The Washington Post)

A black Suburban coasted to a stop in downtown Dallas on Saturday morning, and Mayor Mike Rawlings, in blue jeans and black cowboy boots, stepped out and surveyed the crime scene. Police barricades still blocked Main Street. FBI agents in navy blue T-shirts and khakis combed the street for evidence; one retrieved what appeared to be an ammunition casing.

Rawlings gave some media interviews, then sat down on a park bench. He was still talking in his TV voice: “I’m feeling determined.” And: “I’m feeling like we have a chance to really change things here. I’m feeling . . . ”

His voice trailed off. He lowered his head. He began to cry.

“God,” he said. “I’m sorry. I haven’t cried through all of this. And now I’m sitting here crying on a park bench like an idiot. I’m sorry, I need to compose myself.”

Fifty-three years ago, a sniper assassinated President John F. Kennedy here, and in the national imagination, this became the City of Hate. Civic leaders labored for decades to wipe away that stain.

The city became known for other things, too: The championship football team, the prime-time soap opera “Dallas” and money, glitz and gleaming skyscrapers that soared from the plains of North Texas.

But the horror of Thursday night — five law enforcement officers slain by a gunman at the end of a peaceful Black Lives Matter rally — has once again left the city in shock, searching for explanations.

The protest rally on Thursday, by all accounts, had been moderate in tone, almost a family affair, with protesters and officers feeling at ease, even giving one another hugs — until the chaos erupted.

Rawlings and other city leaders wondered whether the ambush of police was symptomatic of deeper unrest in the city, which continues to have a wealthy, mostly white north side and a poorer, mostly minority southern side.

Or was it the random crime of a madman?

The mayor thinks the latter, but he added, “We’re still debating that issue.”

The protesters have been standing down. They remain committed to their cause and angry that Dallas police officers have not faced charges after shooting black citizens. But they said they did not have an antagonistic relationship with the officers in the patrol units typically assigned to protest rallies.

“The [police] are humans,” Dominique Alexander of the Next Generation Action Network said.

“These officers are a crew that we all recognize from our protests. Of course we are hurting for them.”

One activist, Sara Mokuria, 33, co-founder of Mothers Against Police Brutality, pushed back Saturday against the narrative that Dallas has a model police department. She said she saw her father gunned down by police when she was 10 years old.

“My father was a kind man who had some problems,” Mokuria said. “And the police killed him in front of my own eyes. That’s Dallas.”

She said Dallas has long been image-conscious:

“We have no ocean. We have no mountains. What do we have? We have businesses and shopping, and we want to be a world-class city. We want to be something other than a place where JFK got shot. But we have 1 in 3 children living in poverty, and in some neighborhoods, that is 3 in 3 children living in poverty.”

On Saturday in South Dallas, community leaders gathered at noon to celebrate the 40th anniversary of the unveiling of a statue of the Rev. Martin Luther King Jr. Organizer Candace Wicks said of the shooting: “I don’t think you can make sense of it. But I think the political climate has fed into the polarizing of the races. Now they are acting out in violence.”

Malcolm X and Martin Luther King Jr. are both featured on a mural in Dallas at the intersection of two boulevards named for the men. On Saturday in South Dallas, community leaders gathered to celebrate the 40th anniversary of the unveiling of a statue of King. (Bonnie Jo Mount/The Washington Post)

The Martin Luther King Jr. Community Center is on a boulevard named for King. A few blocks away, it intersects with Malcolm X Boulevard, where a mural shows both men, a sunburst and the word “BELIEVE,” and where a thin woman was passed out cold on the sidewalk Saturday at high noon.

“We still need a Dr. King today. And we still need a Malcolm X today. The foundation is lost. There’s no unified agenda,” said LaRhonda Bacon, the event coordinator at the MLK Center. “Yes, Malcolm X was more an extremist, but his people still worked with a foundation.”

The closed-off crime scene downtown came right to the edge of Dealey Plaza, the site of Kennedy’s assassination.

The mass murder of the police officers has been dubbed the Dallas ambush, or simply “7/7,” after the date of the incident. This city has been quiet, completely flattened by what happened Thursday. This is a time for prayer vigils, the lowering of flags to half-staff and vows to heal.

Before sunrise Saturday, Pastor Joseph Clifford sat at his dining room table, struggling with what message to deliver the next morning to the 1,600 members of First Presbyterian Church in downtown Dallas.

He thought about how the impulse after a tragedy like Thursday’s shootings often is to give in to fear, to hunker down, to withdraw from anyone and anything different.

“There’s far too much that separates us from loving one another,” he said. “The fact that it takes an act of hate to call forth our love, that’s a shame, and the world should not be that way.”

There was also no sign of divisiveness at the makeshift memorial to the slain police officers that has materialized outside the police department’s headquarters on Lamar Street. Two patrol cars are covered with flowers and handwritten condolence notes.

Jacquelyn Walker, 52, an African American born in Dallas two months before JFK’s assassination, has a daughter on the police force, and when she went to police headquarters Friday night, she hugged every officer she saw. “They’re all like my babies to me,” she said. “When we lose one, we all feel it.”

“It’s a sign of the times. All these youngsters are getting killed on a daily basis,” said Kevin Stanley, 49, right, in Dallas. (Bonnie Jo Mount/The Washington Post)

A Dallas native, Robert Ramsden — 44, white and a corporate security manager who lives across from the police department — recalled the city’s reputation after the JFK assassination: “We tried to make it better. That wasn’t us. This isn’t us, either.”

Dorothy Gentry, 50, who teaches language arts at a middle school, came with her 14-year-old son, Jeremiah Bodwin, to pay respects Friday night. Gentry, who is African American, was born on the south side of Dallas when the city was known for police brutality.

“It changed. It changed for the better. Our first black mayor, Ron Kirk. Our first black city manager, Richard Knight. Our first black school superintendent, Marvin Edwards. Those relations, they began to be mended,” Gentry said. But she cited a litany of recent events that angered people: hatred of President Obama, Donald Trump’s divisive campaign, the water crisis in Flint, Mich.

“The frustration boiled over,” she said.

What happened on 7/7 here carried eerie echoes of 11/22/1963. Once again, the sniper shot from on high. Once again, wounded officers were transported to Parkland hospital, where Kennedy was declared dead. Once again, the prime suspect did not long survive. Lee Harvey Oswald was shot and killed on live television while in police custody; this latest gunman was blown up by a bomb delivered by a Dallas police bomb-squad robot.

Once again, the gunman was a former U.S. military man. And once again, this was not an entirely random event, but one that belonged to a historical moment. Oswald probably shot Kennedy out of an ideological fanaticism cultivated in the Cold War.

The gunman who spoke to police early Friday said he was outraged by the recent killings of black men by police officers, including the shooting of Alton Sterling in Louisiana and Philando Castile in Minnesota.

The Dallas authorities initially said Friday that the ambush here was a conspiracy and that there were multiple shooters. But there was no conspiracy. This was another lone gunman who leveraged his extremism with a rifle.

“It’s a sign of the times. All these youngsters are getting killed on a daily basis. And one man said, ‘Screw it,’ ” said Kevin Stanley, 49, a disabled white man sitting in the shade in a wheelchair along Martin Luther King Jr. Boulevard near the MLK Center.

Next to him, a black woman, Lillie Conwright, 79, chimed in: “The Bible said before the end of time there would be a lot of murdering of one another.”

“Civil war,” he said.

“We just have to pray,” she said.