In the early hours of July 24, someone placed a call to Austin’s 911 dispatch. The male caller told the operator he was looking out of his window and saw a teenager who may have had a gun. He wasn’t certain it was a weapon, but the person was “messing with his waistband,” the caller said. He gave the address of a community park in northeast Austin, one with a playground and a basketball court. When police arrived only minutes later, the only pe…