Large groups of unruly teenagers at an Illinois pool and California mall prompted early closures that resulted in arrests, highlighting what experts call a symptom of cultural breakdown.

They say so-called flash mobs are sneaking into apartment buildings at night, taking over community rooms by partying and causing damage.

Dubbed "flash mob robberies," the thefts are bedeviling both police and retailers, who say some of the heists were orchestrated or at least boasted about afterward on social networking sites.

PHILADELPHIA (WPVI) -- Philadelphia police are hoping to shut down the next potential flash mob before it happens. In the digital age of social media, police say there are always new things to learn.

Just over 15 years ago, a flash mob (yeah, remember those) featuring dozens of dancers, Brutus Buckeye and then-OSU president E. Gordon Gee took over the Ohio Union to the tune of a 'Glee' cover ...

If you go The Flash Mob will take place around 12:15-12:45 p.m. on May 23 at the Redondo Beach Pier and continue from 2 to 3 p.m. at the base of the Hermosa Beach Pier by The Strand.

Surveillance video captured a mob of teen bicyclists ransacking a gas station convenience store in L.A.’s Lincoln Heights neighborhood. A group of around 15-20 people targeted a Chevron gas ...

A fleet of cars pulled into a parking lot and a mob of masked raiders poured out of it. They used a pickaxe and sledgehammers to try to smash their way into a jewelry store. What the raiders did ...

Aug. 27, 2011 -- When a massive flash mob rampaged outside the Wisconsin State Fair injuring 11 fairgoers on Aug. 4, old-fashioned police work quickly led to the arrests of 31 people.

Just over 15 years ago, a flash mob (yeah, remember those) featuring dozens of dancers, Brutus Buckeye and then-OSU president E. Gordon Gee took over the Ohio Union to the tune of a 'Glee' cover ...