Whether it’s for an extravagant proposal or just a sing-a-long surprise, entertaining flash mobs typically lift people’s spirits. However, a flash mob in Florida on Saturday night was decidedly more sinister. A gang of about 300 teenagers mobbed a Wal-Mart in Jacksonville where they ran wild, destroyed $1,500 of property, started a food fight and fired gun-shots, according to police reports. Investigators suspect that the massive group could have come on from a party that the police broke up earlier in the night.