Traffic came to a complete standstill as hundreds of people spilled onto Hollywood Boulevard on July 28. They were there to see DJ Kaskade, who promoted his impromptu performance on Twitter. But the so-called "flash mob" got too big, and police had to be called in.
"It's challenging, to say the least. We are trying to make a dent," said LAPD Officer Lyle Knight.
Knight works with the LAPD's Internet Unit, which is designed to intercept events like the one in Hollywood before they happen.
"We try to get some feelers. We don't want to be blindsided," said Knight. "We're trying to make sure we have enough personnel deployed."
Most flash mobs are innocent gatherings. But when hundreds of people gather spontaneously in one location, things can go wrong. And that's when the LAPD's Internet Unit comes into play.
The definition of a flash mob? For example, if someone sends out a tweet on Twitter to 500 of their closest friends to join them at a public square for a dance party. If all they're doing is dancing, the LAPD doesn't care. But if the group becomes disruptive or starts engaging in criminal behavior, that's when the police get involved.
"We're looking for criminal behavior. We're looking for public-safety problems. We're certainly not looking for anybody doing anything artistic," said LAPD Commander Andrew Smith.
The officers in the Internet Unit who scour Facebook or Twitter are looking for any signs of a flash mob that might be planning on something illegal.
"Most of the people who participate in them aren't really trying to do anything bad anyway," said L.A. resident Jamiel Grey.
The LAPD says it's not trying to clamp down on fun. It wants to prevent problems, like when the Internet Unit found out that some people were trying to form a flash mob on the Mullholland Bridge during its partial demolition in July.
"We were able to put extra officers on both sides of the bridge, and when people came to scout it out, they realized, 'Hey, there's too many police out here, we're not going to be able to do our little skit on the bridge this time,'" said Smith.