SAN LEANDRO, Calif. (KGO) -- Local police are warning violent packs of teenagers are attacking and robbing people, seemingly at random. They're calling it "wilding" -- a dangerous trend that first made headlines more than 20 years ago.These attacks happened over the last few days in San Leandro on East 14th and Estabrook streets and near the Bayfair mall.This has been taking place every weekend for the past month and the Bayfair mall has been dealing with a lot of these problems, but it starting to happen more often, including an incident that happened Monday afternoon."Yesterday, I was just driving down southbound on East 14th Street and all of a sudden a gang of juveniles, about 20 to 25, were kind of rowdy in the street, right in front of my car," business owner James Begier said.Begier was witnessing a mob of teenagers, surrounding a couple's car in front of the Pho Anh-Ha restaurant in San Leandro. Police caught two of them."One of the kids that we arrested tried to take a car from the victim, who had a baby in the car, so we arrested him for kidnapping," San Leandro Police Lt. Mike Sobek said.For the past month, San Leandro police say mobs of up to 150 teens and young adults come into the city, on BART, from around the Bay Area, and wreak havoc.On Saturday a mob chased two teens, from the Bay Fair BART station to the nearby mall, where they beat and robbed them.Police believe a YouTube video (warning: contains strong language) taken in Downtown Chicago last year, set off a trend called "wilding." They use social media to organize a flash mob that goes on a rampage."We have a city that we have to deal with, with other calls for service and if you have to babysit and continue to watch these juveniles as they're walking around, it takes up all our resources," Sobek said.This is happening all along the I-880 East Bay corridor, and now a group of cities are preparing to create a police task force to combat the problem.