Bay Area law enforcement authorities and retail officials expressed shock and concern Monday after a string of brash public robberies over the weekend saw groups of people — as many as 80 in one case — swarm stores, grab merchandise and flee while the holiday shopping season is in full swing.

In Oakland, roving caravans of armed robbers hit marijuana dispensaries and other retail shops and pharmacies across the city, often forcing their way in by gunfire, according to police Chief LeRonne Armstrong.

Thieves also struck the Nordstrom store in Walnut Creek, a jewelry store at a Hayward mall, retailers in San Francisco’s Union Square, and a high end clothing store and a sunglasses shop in San Jose. Authorities were looking for any possible links between the cases.

A San Jose police spokesman said the targeting Sunday of a Lululemon shop at Santana Row was “organized robbery.”

“People need to be alert,” said San Jose police Sgt. Christian Camarillo. “We’re coming into the busy holiday shopping season. We can’t be everywhere at the same time. We do need citizens’ help; when they see suspicious activity occurring, please let us know, especially at the malls.”

The spate of crimes began around 8 p.m. Friday evening, when thieves descended on stores in San Francisco’s Union Square, home to many luxury retailers. Videos posted to social media showed robbers fleeing the Louis Vuitton store with arms full of merchandise, heading to waiting cars while police ran in pursuit and detained at least one suspect.

Police said they had arrested several people and were “controlling and limiting” traffic around Union Square on Sunday to discourage further thefts.

Across the Bay, “hundreds” of vehicles targeted marijuana shops across Oakland on Friday, Armstrong said. Officers said more than 175 shots were fired by the robbers, forcing officers to draw back to safe locations.

“We’re not going to tolerate this type of activity within the city of Oakland,” Armstrong said. “We’re going to respond.”

Roughly 24 hours later, on Saturday night, dozens of thieves ransacked the Nordstrom store at Broadway Plaza in Walnut Creek during what police called an “organized” and “planned” robbery. Approximately 80 people were involved in the incident, which occurred shortly before 9 p.m. when Nordstrom and other stores at the shopping center were still open. Two store employees who were assaulted and a third who was pepper-sprayed were treated at the scene. Three people were arrested.

Just after 11 p.m. on Saturday, another round of “roving caravans” hit Oakland, targeting at least two dozen businesses including retail shops, pharmacies and marijuana shops. One person was wounded when a shootout erupted between the robbers and a security guard at one of the dispensaries, police said. 

At least seven people have been arrested in connection with the Oakland robberies, said Kim Armstead, a police spokeswoman. She did not have information about their identities or any suspected charges

On Sunday, three businesses in Hayward and San Jose were hit: A group of robbers used hammers to smash open cases at a Sam’s Jewelers store at Southland Mall in Hayward, grabbing jewelry and escaping in multiple vehicles.

A short time later, at least four people stole more than $40,000 worth of merchandise from the Lululemon store at Santana Row, police said. Around the same time, a group took about $7,000 of merchandise from a Sunglass Hut at the Westfield Valley Fair mall, escaping in four or five vehicles with covered license plates. One of the men at the Lululemon robbery had a “visible gun in his waistband,” police said.

Police throughout the region were taking measures to prepare for the possibility of more incidents. Walnut Creek city spokeswoman Betsy Burkhart said. Police Chief Jamie Knox had already reached out to the FBI, the California Highway Patrol and the U.S. Marshals Service, she added.

Malls were taking precautions as well.

“Here at Oakridge we have been in talks with SJPD to get some off-duty officers to work onsite,” said Anthony Howell, marketing manager for the South San Jose mall owned and operated by Westfield. “In addition, we had a retailer meeting today with SJPD to discuss different strategies and how to deal with shoplifters and loss prevention.”

Authorities said the attacks were coordinated and planned, an aspect that only makes it tougher for police to respond.

“No city can be prepared for one day, with no notice, 80 people committing an organized theft within one minute,” Walnut Creek mayor Kevin Wilk said of the Nordstrom attack.

Social media likely has proven an effective organizing space for thieves, according to Rachel Michelin, the president of the California Retailers’ Association.

“I think we’re seeing more and more use of social media that can coordinate these brazen crimes,” Michelin said. “In addition, we’re seeing more and more of these products showing up on online marketplaces.”

Gov. Gavin Newsom offered assurances Monday that California will look to crack down on retail theft, adding that the state has had a retail theft task force working with cities and counties along with the CHP.

“We’ll be stepping up those efforts in next year’s budget entirely,” he said during a COVID-19 media briefing in San Francisco. “And we have been working with cities up and down the state … that were impacted over this weekend by these organized retail theft operations.”

Michelin said the San Francisco and Oakland areas suffer the second-highest amount of losses to organized retail crime in the country, a figure she put at about $3.6 billion. Along with it, she said, came $275 million in lost sales tax revenue to local municipalities and the state.

She said that more must be done to hold thieves responsible and that people “must start seeing consequences.”

Newsom said it’s coming.

“Look, I have no sympathy, no empathy whatsoever, for people smashing and grabbing, stealing people’s items, creating havoc and terror on our streets. None. Period. Full Stop,” he said. “We want real accountability. We want people prosecuted. And we want people to feel safe this holiday season.”

Staff writers John Woolfolk and Linda Zavoral contributed to this report.