Police say three youths have been arrested, and a fourth was being sought after a gunshot led to the evacuation of a shopping mall in northwestern Indiana.  The bullet from a Russian-made 7.65 mm handgun lodged in a ceiling did not strike anyone Saturday at the Westfield Southlake mall in Hobart, just outside of Gary.  Hobart Police Chief says off-duty officers working security at the mall swiftly apprehended three boys ages 14, 15, and 16. The boys were the aggressors in a fight with another group of boys.