A wild flash mob stormed and trashed a Brooklyn mall, causing so much chaos that the shopping center was forced to close during post-Christmas sales, sources said Friday.

More than 400 crazed teens — who mistakenly thought the rapper Fabolous would perform — erupted into brawls all over Kings Plaza Shopping Center in Mill Basin on Thursday at 5 p.m., sources said.

The troublemakers looted and ransacked several stores as panicked shoppers ran for the exits and clerks scrambled to pull down metal gates.

“I was begging them to stop. There were a lot of kids, hundreds of kids . . . [Security] would chase them out one door and they would come back in another door,” said Abu Taleb, 31, a clerk at the kiosk Candy Plaza 2. “I’ve been here seven years, and I have never seen anything like this before.”

Some of the teens staged a game of “knockout” on the top floor — and one may have been carrying a gun, sources said.

“They were playing the ‘knockout’ game,” said Shante, a 21-year-old perfume merchant, in reference to a violent trend in which teens try to knock out an unsuspecting victim with a single punch.

“People were getting really scared,” she said.

The mall was shuttered at around 7 p.m. for roughly an hour and has since issued a temporary “no teens” rule, in which anyone under 21 must be accompanied by an adult, police sources said.

Fights at the mall also broke out in front of McDonald’s and Best Buy, where a group of girls began screaming and throwing punches as security guards struggled to break up the brawl.

Two security guards also carried a teenage boy out by his wrists and ankles, video footage shows.

Some of the teens — who had planned the rowdy meet-up on social media — later took to Facebook to brag about it.

“[Kings Plaza] was on tilt today but n-ggas wasn’t catching me,” Ray Ray Sextana posted on Facebook.

Another teen, Mark Wallace, posted, “S–t was crazy at Kings Plaza. So the security started shutting down the mall and kicking all teens out but it was so much of us they couldn’t get control.”

He added,“F–ked up my middle finger tryna fight them bitch ass security guards.”

Nobody was injured seriously and no arrests were made, police sources said. A fight broke out at the same shopping center during a 2010 Fabolous appearance.