CHICAGO (CBS) — Unbelievable surveillance video captured flash mobs dashing into store after store and running out with armloads and sometimes entire racks of sporting goods.

It has happened at three different Sports Authority stores in the Chicago area.

This past Monday in Burbank at just before 1 p.m., five individuals entered a Sports Authority and soon after they were off. Video shows them running out the door with rack after rack of apparel and an employee giving chase.

On Saturday at a Sports Authority on Clark Street, a half dozen entered and stole several racks with lighting fast speed.

The store chain sounded the siren, saying, “At Sports Authority, the comfort and safety of our employees and customers always remain our top priority.”

UPDATE: Retailer Takes Steps To Deter Flash Robberies

It’s like a next-generation flash mob. Originally, flash mob referred to a group of people doing a performance to draw attention to something in a positive way. The term gave way to a more sinister motive.

“They used to just be fun. They used to just be positive and now, I don’t know, it seems to have turned into something negative,” said one shopper.

No one was hurt in the three incidents, though it’s clear the mob stops for no one.

A close look at the robbery on Clark Street shows an employee who tries to intercede gets trampled.

The third incident occurred at the Frankfort location.

There have been no arrests so far and Sports Authority is offering a $5,000 reward for information that leads to an arrest.

The chain on Thursday discussed plans to deter future robberies.