There were to be jugglers, stilt walkers and puppets of giant butterflies, all marching down Maple Avenue in South Plainfield, New Jersey, in the town’s 62nd annual Labor Day parade.

Instead, as it started to rain today, the festivities were abruptly canceled, not because of the weather, but because of something that now seems as common at this summer’s public gatherings as hot dogs and fried dough: fear.

Police had found explosive devices overnight near the home of a man who lived close to the staging area of the parade route, said Matthew P. Anesh, the mayor of South Plainfield, a town about 35 miles southwest of New York City, at a news conference Monday afternoon.

The devices did not appear to be bombs, but were closer to homemade fireworks, according to a person familiar with the situation who requested anonymity because he was not permitted to discuss the ongoing investigation.

The parade had never been a target.

Thomas G. Kaiser, 55, was arrested and charged today with possession of a destructive device for an unlawful purpose, according to the Monmouth County prosecutor’s office.

“I can’t say that they overreacted because there is so much going on in the country right now, you can’t overreact, you just can’t,” said Paul Fessock, whose band, Amp’d, was scheduled to play a concert at Spring Lake Park after the parade. Fessock said he agreed with the town’s decision to shut down the festivities.

That the scare canceled the parade, in which Gov. Philip D. Murphy and his wife had been scheduled to march, as well as the charity fun run and evening fireworks, was a painful coda to a summer pockmarked by anxiety.

The country’s most prosaic gathering spaces have been the targets of murderous gunmen in recent weeks. There have been mass shootings at a garlic festival in Gilroy, California, on the highways and in a Walmart in El Paso, Texas.

“With all these bad things going on, as soon as you hear something, it’s so close to home and you wonder, ‘Is it coming here, too?’” said Severino Baratta, the owner of Ciccio’s Pizza on Maple Avenue.

Three years ago, New Jersey faced an all-too-real bomb scare, when an explosive was detonated at the site of the U.S. Marine Corps charity race in Seaside Park, N.J., a beach town about an hour south of South Plainfield.

That bomb and two others set in Manhattan had been planted by Ahmad Khan Rahimi, a New Jersey resident and jihad-inspired terrorist, who was sentenced to two life terms in prison last year.

“These are not the Labor Day activities we would have liked to see today,” Anesh said at the news conference, adding that police with K-9s had spent the night searching the municipal pool and athletic fields. “We were looking forward to today for many months.”

On social media, residents mourned the cancellation of a joyful summer rite. “How do parents explain this to their children? What about the kids who were planning to march today?” a woman named Susan Mazzeo wrote on Facebook. “Today’s world is a scary place!”

Kaiser had come to the attention of police in the town of Sea Bright, on the Jersey Shore, the day before the parade, according to information from the Middlesex County prosecutor’s office, which said he left a package with a destructive device at a popular bar there called Donovan’s Reef. An investigation led to Kaiser’s home in South Plainfield, where more devices were found nearby.

“Everything is being falsified from a little piece of news that just blew up,” a man who identified himself as Kaiser’s brother said in an interview with 1010 WINS radio. “It’s one firework. I know they are illegal in the state of New Jersey; he knows they are illegal in the state of New Jersey, but it’s a firework!” he said, referring to his brother. “It’s not a bomb.”

Today, the stretch of Maple Avenue where floats and the South Plainfield High School Marching Band should have been parading was not looking celebratory.

But the town was already at work on rescheduling some events, according to the mayor, though it was unclear if a parade would be among them.

But whenever it is that Labor Day will again be celebrated in South Plainfield, Fessock of Amp’d said his band would play. “You can’t stop rock ‘n’ roll,” he said.

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