Groups of thieves, some carrying crowbars and hammers, smashed glass cases and window displays and ransacked high-end stores throughout the San Francisco Bay Area, stealing jewellery, sunglasses, suitcases and other merchandise before fleeing in waiting cars during a weekend of brazen organized theft that shocked holiday shoppers and prompted concerns about the busy retail season.

The thefts are believed to be part of sophisticated criminal networks that recruit mainly young people to steal merchandise in stores throughout the country then sell it in online marketplaces. The thefts are ratcheting up as the holiday shopping season gets underway, experts and officials said.

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“We’re not talking about someone who needs money or needs food. These are people who go out and do this is for high profit, and for the thrill,” said Ben Dugan, president of the Coalition of Law Enforcement and Retail.

The weekend robberies started in San Francisco Friday around 8 p.m., when packs of people broke into stores including Louis Vuitton, Burberry and Bloomingdale’s in the downtown area and in Union Square, a posh shopping district popular with tourists that was teeming with holiday shoppers.

Videos of the chaotic scene posted on social media by witnesses showed police officers dragging one suspect from a waiting car and people running with merchandise in their arms or dragging suitcases.

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The flash mobs are usually organized by local people who recruit their crews and send them to steal specific merchandise requested by criminal organizations throughout the country, Dugan said.

Those who do the stealing get paid between $500 and $1,000 to take as much as they can and bring it back to organizers who ship it to other parts of the country.

“Crew bosses organize them, they’ll give him the crowbars, and in some cases even rent them cars, or provide them with escape routes or a list of products to actually go out and steal. It looks very chaotic but it’s actually very well organized,” Dugan said.

Gov. Gavin Newsom said his office met with retailers over the weekend who asked for more police patrols.

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“You will see substantially more starting today, in and around areas that are highly trafficked and coming into the holiday season Black Friday in shopping malls,” he told reporters Monday at an event in San Francisco.

He said the California Highway Patrol immediately stepped up patrols along nearby highway corridors following the thefts this weekend and asked local officials how they could help.

In July, Newsom signed a law that allows prosecutors to charge those who work with others to steal merchandise. He said this year’s state budget included millions of dollars for local officials to address retail theft and his January budget proposal will include an “exponential increase of support to help cities and counties.”

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“My business has been broken into three times this year,” he said. “I have no empathy, no sympathy for these folks, and they must be held to account.” Newsom owns two wine shops in San Francisco.

Most of the flash mob robberies had been happening in stores near highways in suburbs where police response can be slower. But last year, the packs of robbers took advantage of protests following the murder of George Floyd by police in Minneapolis and ransacked stores in several cities, including San Francisco, Dugan said.

Retailers lose about $65 billion each year to organized theft, the bulk stolen by professional thieves. Criminal flash mobs are part of a growing national trend, he said.