WATCH: Bieber fever runs wild on Dean Street

WATCH: Bieber fever runs wild on Dean Street
Associated Press / Bizuayehu Tesfaye

Ladies and gentlemen, Justin has left the building — and now the neighborhood’s a mess.

Hundreds of screaming Justin Bieber’s tweeny-boppers mobbed the pint-sized singer’s bus as it was leaving the Barclays Center on Monday night, blocking sidewalks and traffic and making an awful racket as they chased it down the street — and police could do nothing to stop it.

“I didn’t anticipate this type of crowd or this hysteria over a performer,” said Dep. Insp. Michael Ameri, commanding officer of the 78th Precinct. “It caught me by surprise a little bit.”

As the concert let out around 10 pm, hundreds of Bieber’s young fans swarmed near a VIP parking space next to the loading dock at the back of the arena on Dean Street near Sixth Avenue.

Police corralled the fans into an area near the bike racks on Dean, and urged them to keep the sidewalk clear, but things got crazy when a black bus that super fans identified as Bieber’s pulled out of the loading dock shortly after 11 pm.

Shrieking fans chased the vehicle down Dean past Sixth Avenue, ignoring the pleas of Barclays Center security guards and NYPD officers.

“Justin!” they screamed.

At one point, the bus stopped on Dean Street near the ball field between Sixth and Carlton avenues, and was overrun by fans who leapt in front of it in the street.

A few fans said they saw Alfredo Flores, a member of Bieber’s flock, taking pictures of them from the bus.

“Oh my gosh, I touched him!” one fan screamed, after the door of the bus opened. “I touched Alfredo!”

Peter Krashes of the Dean Street Block Association said the “Hard Days Night”-worthy frenzy disrupted the neighborhood and went against the Barclays Center’s agreement with the community.

“Kids were screaming until midnight,” he said. “We’ve always been told it’s not supposed to be happening near residents. There is a huge plaza on the other side of the arena.”

He also claimed that security and post-concert crowd management has deteriorated since the arena’s opening, when the Barclays Center drew mostly rave reviews for blending relatively smoothly into the neighborhood.

“The police presence and arena security has been reduced,” he argued. “Last night it went too far; there was not enough police presence and the security that was there was overwhelmed.”

Representatives from the Barclays Center declined to answer questions about whether arena security personnel had been reduced since the opening.

The show itself — one that Bieber entered by dropping down from the rafters with a pair of gigantic silver wings — failed to draw rave reviews from those outside the Belieber spell.

“His dance moves lacked energy, his singing showed no passion,” wrote Buzzfeed’s Katie Notopoulos, who called Bieber’s performance “wooden,” “flaccid,” and “rote,” though she chalked it up to his recent break-up with actress and singer Selena Gomez.

Still, the Beliebers begged to differ.

“Bieber in Brooklyn was one of the best things I’ve ever experienced,” wrote a Twitter user named Mia C.

The incident left the area’s top cop vowing he’ll be more prepared the next time a golden-voiced teeny-bopper plays Brooklyn’s new arena.

“Next time Justin Beiber comes to town, we’ll have a better plan,” Ameri said. “Thank god nobody got hurt.”

Reach reporter Eli Rosenberg at [email protected] or by calling (718) 260-2531. And follow him at twitter.com/emrosenberg.