(CNN) -- This week in Germantown, Maryland, it took less than a minute for a flash mob of teenagers to descend on a 7-Eleven, ransack shelves and make off with hundreds of dollars worth of stuff.
It's going to take much longer for police in Montgomery County to figure out how to prevent it from happening again.
"We had always thought flash mobs happen in big cities. We are unprepared. We don't have anyone who has social-media expertise," said county police spokeswoman Janelle Smith. "Even if we did, our budget looks like every other law enforcement agency in the country. It's not pretty."
Police in Maryland are not alone in their scramble to find creative, affordable and efficient ways to fight mayhem from flash mobs -- groups of people who gather in one location quickly after being summoned online. Law enforcement in big cities and small towns are all scrambling to, as Smith put it, "catch up with teenagers" when it comes to monitoring crime planning on the Web.
This summer, spontaneous incidents of group violence -- dubbed "flash robs" -- have happened in Minneapolis, Chicago, Cleveland, New York and Washington, among other cities. Most episodes involved groups of young people looting stores or assaulting pedestrians and then running off.
Authorities said they believe at least some of these incidents were triggered by calls on social-networking sites to meet up and wreak havoc, although they cannot say for certain.
By far, the worst flash-mob violence has occurred over the past few weeks in the United Kingdom. Angry hordes terrorized neighborhoods in London, Birmingham and elsewhere. Buildings were torched. People were beaten. Homes were vandalized and looted.
British authorities said the rioters communicated their intent for destruction through BlackBerry Messenger, a private mobile-messaging system that's popular with young people in the UK. One reported text read: "If you're down for making money, we're about to go hard in east London."
Police playing catch-up
At least one expert believes most members of law enforcement are far behind the times when it comes to battling flash robs.
"Part of the challenge is generational. Older officers in management positions -- the ones making decisions -- are often not as savvy as younger officers with social media," said Nancy Kolb, who oversees the International Association of Chiefs of Police's Center for Social Media. "It's important to empower your younger officers, or those with expertise, to teach everyone else."
Many authorities said they believed for years that flash mobs were not a threat. The impression among officers was that flash mobs were harmless groups of strangers responding to a text or e-mail inviting them to gather to perform a cute choreographed dance routine in a public place, Kolb said. Witness the recent AT&T commercial about an ill-timed flash-mob dancer in New York's Grand Central Terminal.
More than 70% of responding agencies also said they had not identified any goals for officers' use of social-media tools such as Facebook and Twitter, even though the vast majority of law enforcement officers were using them. Sixty-six percent of respondents said they had received no training in how to use social media.
When the group's Center for Social Media opened about a year and a half ago with Justice Department funds, flash mobs had only begun to show a dark side. Today, investigators are asking themselves: Why did flash mobs seem to go suddenly from fun to frightening?
Jeff Gardere, a California psychologist who lectures widely on the motivations of young people, said he's not surprised by the shift.
"We're at a point where everyone understands the power of a flash mob," he said. "People inevitably started thinking this was accessible to them, and of course it is -- everyone has a phone."
Gardere said he believes that part of the reason flash mobs have gotten violent is that young people are discontent and bored. They don't have jobs. They hear their parents talking about the lack of jobs. They feel their options are winnowing every day.
"This isn't just in England or Philly or Germantown but everywhere," Gardere said. "You've got a group that feels angry and powerless, and they're trying to assume a sense of power."
A curfew in Philadelphia
Until recently, most law enforcement officials assumed flash mobs only happened in large cities. "It was Philadelphia who had the problem -- that seemed to be the thinking," Kolb said.
Since the spring of 2010, police have reported a series of violent flash-mob incidents in central Philadelphia. In one episode last year, a crowd of some 200 lawbreakers, mostly teenagers, roamed the streets robbing bystanders and breaking windows. Authorities suspect the group gathered after seeing a call on Facebook or Twitter to meet up.
Last month another flash mob of about 30 teens allegedly beat two apparent bystanders near Philadelphia City Hall, knocking one unconscious and breaking another person's jaw. That incident came just weeks after a gang of youths, who Philadelphia authorities say were stoked by a call on social media, attacked diners leaving restaurants and robbed train passengers. Other flash robbers swarmed stores, grabbed what they liked and walked out.
The violence prompted Mayor Michael Nutter and police to enforce a citywide curfew mandating that anyone under 18 be indoors by midnight. Parents of violators would be fined $500, they warned.
Law enforcement experts believe that has been the most significant step to date in calming flash mobs . Philadelphia police investigators also have been friending younger Philadelphians on Facebook in the hopes of monitoring chatter about potential mayhem.
"The curfew idea was a great one, but temporary. The Facebook idea is where we need to go," said Los Angeles County Sheriff's Capt. Mike Parker, a leading expert on how law enforcement should use social media to fight crime.
Name the social-networking site, and Parker has used it to help track down a criminal or do a background check. The skill he most often teaches other officers is how to recognize a Facebook posting or a Twitter hashtag that suggests flash-mob planning is under way.
'Flash calling' and The Game
Parker is helping lead the Los Angeles County Sheriff's Department investigation of hip-hop artist The Game, who sent a Twitter message last week that contained the phone number to a sheriff's station. Hundreds of the rapper's 580,000 Twitter followers overwhelmed dispatchers with calls, effectively preventing the public access to emergency help.
The Game apologized for his tweet on CNN on Wednesday. It's unclear if he will be charged.
That raises another question for law enforcement -- how should a person who encourages mayhem in a tweet be treated by the justice system?
UCLA law professor Eugene Volokh said he believes they should be prosecuted the same way as someone who incites violence in person.
"We don't need to create a new set of laws for an old set of problems," Volokh told CNN.
But Parker said police don't have a solution yet on how to stop flash calling.
"Just when we thought flash mobs were a problem, we have this to deal with," the sheriff's captain said. "But that's technology. There's always going to be something (new)."
Authorities fight back online
Many law enforcement agencies across the country are financially strapped and understaffed. In Los Angeles County, the sheriff's department has lost 500 officers recently to budget cuts, Parker said.
Parker recommends that local agencies pool staff and budgets to train officers on social-media tools. He also suggests they set up websites for posting video -- such as surveillance-camera footage of a suspect -- that authorities want the public to see, promoted through the department's Twitter and Facebook accounts.
"This is so basic, but if you know there's going to be a dance, you have to get on the invite list," Parker says. "You have to be on these sites -- Facebook, Twitter, Foursquare, Flickr -- with the mindset that you're not just watching passively. You're engaging."
Parker urges fellow officers to network with citizens on Facebook and Twitter as a way of monitoring chatter and increasing cooperation with police.
"Make yourself a friend, approachable. You have to position yourself in a way that isn't threatening, because we really are not there to shut down anyone's fun," he said.
Parker said the online chatter about flash mobs is often full of boasting. Would-be flash mobbers usually assume the police are the enemy, he said, so they amp themselves up for a fight.
"If you see that, try to get involved in the discussion and dispel it," he said. "It's all basic communication. Let me try to understand you, and you try to understand where I'm coming from."
Police in Maryland acted quickly and creatively after the 7-Eleven robbery. Within hours, investigators posted surveillance camera footage on YouTube and blasted out that link on local media.
Detectives then headed to a local high school, where they asked the principal and students to help them identify faces. Within a day, they had identified at least half of the alleged thieves, said Smith, the police spokeswoman.
No arrests had been made as of Thursday morning.
"But we feel confident," Smith said. "Technology and old-fashioned police work are on our side."