California officials on Monday were investigating a bizarre weekend robbery at an Oakland train station, in which a mob of between 40 and 60 teens targeted train passengers in a coordinated attack around 9:30 p.m. Seven people were robbed at the Oakland Coliseum BART station, and some of them were punched or otherwise injured, police say. The youths jumped the fare gates Saturday night and many of them boarded the train, demanding purses, phones, and duffel bags. None of the victims or witnesses reported seeing guns or weapons during the attack, which lasted about five minutes before the group bolted, authorities said. All of the suspects are minors, but officials have not released detailed descriptions or an age range.