Howard Prager, 66, and his klezmer band were set up in chairs on a slow-moving flatbed truck Monday morning as they pulled into the Highland Park Fourth of July parade lineup.

A parade hadn’t been held in three years, since before the pandemic. “Everyone was so relieved to be out,” he told reporters.

Maxwell Street Klezmer Band began with an upbeat song, one fit for weddings and celebrations. That’s when they noticed people fleeing.

Prager initially assumed there was a celebrity or something in the parade they were running to see.

“Then I noticed the panic on their faces,” he explained. “We saw mothers and fathers pushing strollers. We came across adults. We saw a lot of teenagers. And they’re all heading in the same direction. A gunman opened fire on a parade in Highland Park, a Chicago suburb, around 10 a.m. Monday, killing six people and injuring dozens more. Residents were advised to stay put for the duration of the search. Authorities said a person of interest was apprehended Monday evening.

After the shooting, the family-friendly event was transformed into a crime scene, with abandoned lawn chairs, wagons, and bikes strewn along the parade route.

Alexander Sandoval, 39, a contractor, shook his head as he described the incident to his 5-year-old son, his partner, and her 6-year-old daughter. At 7 a.m., three hours before the festivities began, he had set up chairs in front of the stage.

“We thought it was the Navy saluting the flag when everything started happening,” he told USA TODAY. “Shots were fired. I grabbed my child and bolted.”

The parade is part of a daylong celebration in Highland Park, an affluent Chicago suburb known for its leafy suburban streets.

The digital archives of the Illinois State Library show annual pictures of floats towed behind station wagons dating back to at least the mid-1960s. The historical society poses in one. In another, an honor guard stands at attention as a mobile Iwo Jima statue rolls by.

According to their website, the Maxwell Street band has been performing with a growing cast of members since 1983. The band’s website claims that, in addition to weddings and bar mitzvahs, it has toured as far as Carnegie Hall and Europe. The band has a diverse lineup of more than 20 members. They used seven musicians for the parade setup, according to Prager: violin, trombone, clarinet, trumpet, an electric piano, drums, and Prager on tuba.

The parade follows a dogleg down the street next to Highland Park Public Library. The parade turns the corner for its run down Highland Park’s main drag, where the shooting began, at the next block, where the storefronts of Central Avenue begin.

At about 10:15, the band launched into a song Prager’s sheet music calls “Freilechs fun der chuppeh” – freilech, Prager said, meaning a joyous person; the chuppeh, or chuppah, the canopy for a Jewish wedding ceremony.

They hadn’t even arrived at the corner of Central Avenue when they noticed the people fleeing. “I recognized and heard pops of the gun and thought, oh my gosh, this is something serious,” he said.

“You’ve seen disaster movies and things where people are fleeing. “It felt exactly like that,” he explained. “Like we were right in the middle of it.” People are rushing past us.”

They had to get out of there, but their truck was trapped. The driver had no idea where he was going. Finally, he said, they turned around and returned to their starting point through an opening in the crowd.

They were numb, in shock, and unsure what to do next, so they did what bands do: they went to their next gig in Skokie. But, like so many other nearby events, it had been canceled.

By the evening, Prager was speaking for his bandmates and reflecting on how the shooting had altered the Fourth of July.

“All I want to see is something that brings us all together and makes us whole again,” he explained. “I’d like to see this country come together and realize that we all believe in liberty, freedom, and peace for all.”