The annual “Fright Fest” at Six Flags Great America in Illinois became a real-life nightmare for a family of three who was attacked after a line-cutting dispute with a group of teens, police said.

The harrowing ordeal unfolded after the rowdy teens cut in front of a 50-year-old woman standing in line with her husband, 51, and their 12-year-old son at the Gurnee amusement park on Saturday, the Chicago Sun-Times reports.

The woman asked the group to stop using foul language before one of them “sucker-punched” her son, Gurnee Deputy Police Chief Brian Smith told the newspaper. The pack of teens then pummeled the family, dropping them on the floor.

The family had “significant injuries,” Smith said. They were taken to a hospital and have since been released, he said Wednesday.

Gregory Battle, 18, was arrested and charged with aggravated battery causing great bodily harm, mob action and aggravated battery in a public place. He was released from jail after posting $20,000 bond before his initial court appearance in Lake County on Wednesday. He declined to comment when contacted by the newspaper via social media, the Chicago Tribune reports.

Battle allegedly took part in the assault, but is not believed to have thrown the first punch, Smith told The Post. One of the juvenile teens is believed to have started the assault, he said.

Eight other teen suspects — ages 15 to 17 — received juvenile petitions for mob action and were taken to a juvenile complex center in Vernon Hills, according to the Chicago Tribune.

The annual Halloween-themed event at the park usually attracts an “increased number of knuckleheads who come to stir things up,” Smith said, but Saturday’s incident was outside the norm.

“This is rare,” Smith told the Sun-Times. “This is on a different spectrum. This family is lucky they got out with just the injuries that they did.”

A spokeswoman for the park said the incident was “isolated” and that security officials responded accordingly.

“The safety of our guests and team members is always our highest priority and we have zero tolerance for any unlawful behavior,” park officials said in a statement to The Post. “We continually adjust our security measures to maintain guest safety and well-being. We partner with local police as well as staff our own robust security team and work in unison with other entities to maintain a safe environment.”

Police, meanwhile, are asking the public for any video of the alleged attack. Footage retrieved from the park was “not very conclusive” since most of the melee was blocked from view, Smith told The Post.

“We’re looking for as much as we can get in terms of video,” Smith said. “And there were a lot of phones out, according to witnesses.”