A military Humvee on display at a Farmingville festival suddenly careened down a hill and into a crowd of people Saturday evening, seriously injuring a woman, police and witnesses said.

Suffolk County police said the vehicle “came out of gear” at the Long Island Bacon Bash about 5:10 p.m., rolled down the embankment and struck Suzette Lamonica, 46, of Brookhaven, pinning her against a food truck.

The hulking U.S. Army Reserve Humvee was a popular attraction at the festival at the Pennysaver Amphitheater at Bald Hill, drawing a line of parents with wide-eyed children in tow.

A Coram couple who allowed their 5-year-old son to sit in the Humvee was stunned when, a few minutes later, the vehicle started moving, sending onlookers scrambling and screaming.

Jeremy Araujo said the Humvee’s powerful engine wasn’t running and he examined the wheels to make sure they were secure before letting his son, Jaxson, climb on.

“There was a bunch of kids in it, and it looked sound and safe,” Araujo, 36, said. “Then we’re leaving and we’re about 20 feet away, and there was a loud commotion and people screaming.”

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Araujo said he and his wife, Dayna Bradley, turned back to look and saw the injured woman drenched in blood and several other people lying on the ground.

Bradley, 42, said they covered Jaxson’s eyes and ran to their car.

“We literally pulled our son off like 30 seconds before,” Araujo added.

Police said the Farmingville Fire Department rushed Lamonica to Stony Brook University Hospital with serious arm and leg injuries.

Richard Gherardi, 30, of East Hampton, was also taken to the hospital for treatment of burns, police said. He was in the food truck when it was struck by the Humvee and was splashed with hot cooking oil.

Two other women received minor injuries but declined treatment, police said.

Security staff abruptly shut down the festival, turning people away at the entrance and ushering attendees out.

The Humvee was impounded for a safety check. Police are asking anyone with information about the accident to call 631-854-8652.

The event had been scheduled to run from noon until 10 p.m., but the site was deserted except for police by about 7:30 p.m.

Farmingville Fire Department officials and event organizers could not be reached for comment.

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Besides a variety of bacon-infused foods, the festival offered live music and a long list of vendors. A portion of the proceeds was to benefit Long Island Cares.

The Pennysaver Amphitheater is owned by the Town of Brookhaven. A town spokesman did not immediately respond to a request for comment.