Was it a flash mob that forced the closure of North Avenue beach on Memorial Day? Chicago Police News Affairs released a statement saying they had to close the beach for safety reasons, as people were suffering heat exhaustion and emergency vehicles couldn't get through to help. But, WLS listeners say there was what they called a "large gangbanger element" at the Oak Street and North Avenue beaches. READ: Emanuel: Police made right call in closing beach Listeners report being at the beach, and seeing dozens of gang bangers pushing people off their bikes. Another listener says those causing havoc...