DALLAS >> The leadership of the Next Generation Action Network drove all night from Baton Rouge, Louisiana, arriving in Dallas early on July 7, just hours before the start of their hastily arranged march that ended in the worst attack on law enforcement since 9/11.

Dominique Alexander, a 27-year-old Baptist preacher and the civil rights group’s founder, said that after the shooting deaths by police of Alton Sterling in Baton Rouge and Philando Castile in Falcon Heights, Minnesota, hundreds of messages poured into the group’s shared email and social media accounts, asking whether Dallas would hold a protest like those in Baton Rouge and Minneapolis. Black Lives Matter, which organized the other marches, doesn’t have a Dallas chapter.

“We should do this. We’ve got 24 hours. Let’s go,” Alexander recalled telling his companions on the trip, Next Generation’s attorney and its chief of staff.

So as they made their way to Baton Rouge to meet Sterling’s aunt, Alexander advertised on social media a rally the following day in downtown Dallas. Within hours, he said, more than 800 people had indicated they were coming, with another 800 marking themselves as “interested” on the march’s Facebook event page.

“You rally off that hype. If it’s just the right timing, you get a burst. You can get a stampede,” said Alexander, among the young activists who are leading a new civil rights movement in Dallas.

The Next Generation Action Network has held more than 50 protests against police brutality since the group was founded in August 2014 after the death of Michael Brown in Ferguson, Missouri. Most of the protests have drawn small crowds.

So it surprised Alexander and the march’s co-organizer, fellow Baptist minister Jeff Hood, to see downtown Dallas flooded with people. They celebrated the proof of their movement’s vitality — until they heard shots fired.

At the end of the march, Micah Johnson, a 25-year-old Army veteran, trained his assault weapon on Dallas police, killing five officers and wounding nine others and two civilians. In an hours-long standoff with police that ended with his death, Johnson said that he wanted to kill officers, specifically white officers.

The shooting exposed a rift many people in Dallas thought had been healed decades ago.

Dallas, like many cities in America, remains divided along racial lines. Predominantly poor black and Hispanic neighborhoods are cut off from the rest of the city by three intersecting highways. A quarter of the city’s 1.3 million population lives in poverty, mostly on the city’s South Side, census data show.

South Dallas is home to some of the largest megachurches in the U.S., but large tracts remain empty and run-down, in stark contrast with the gleaming skyscrapers and expensive hotels north of Interstate 35.

Otherwise disparate groups of young local activists — many of whom grew up on the South Side and have lost family or friends in police-involved shootings — have coalesced around the issue of police brutality, reviving a civil rights movement in a city whose leaders often tout its progress with diversity.

Yafeuh Balogun, 32-year-old co-founder of the group Guerrilla Mainframe, a community group that hosts cookouts and political discussions in Dallas’ poorest neighborhoods, started out with a mobile vegetarian lunch counter that he would park in the middle of low-income apartment complexes.

After activist Stephen Benavides, 35, produced a report in 2014 based on 10 years of public data that showed a disproportionate number of Dallas police shootings involved black and Hispanic male suspects, Balogun said he “began to take more of a militant position.”

Balogun and the People’s New Black Panther Party co-founded the Huey P. Newton Gun Club, a coalition focused on self-defense and named after a co-founder of the Black Panther Party. The club provides armed patrols and training exercises and takes people from poor, minority communities to local gun ranges.

These younger activists see themselves filling a void, as they say influential black church leaders in the area have not done enough to galvanize people.

Although their tactics are different, Alexander and Balogun are united in pressing for policy changes at the Dallas Police Department and placing greater emphasis on security at their events in the wake of Johnson’s attack.

Meanwhile, Benavides’ group, Dallas Communities Organizing for Change, is awaiting a response from the U.S. Department of Justice to a complaint it filed in late 2014 alleging that Dallas police have engaged in a pattern of excessive use of force against black and Hispanic suspects.

On Aug. 10, Alexander will lead a march to Dallas City Hall to demand the revocation of a policy that gives officers involved in shootings 72 hours before they have to give a statement and to urge subpoena power for the citizen police review board.

“Whether the organization gets seven or 1,000 people to come out, all we do is say, ‘Hey, we’re going to be in the forefront,’” Alexander said.