Suspected gang members shot down a helicopter in a clash with police in restive western Mexico on Tuesday, killing four people, the governor of the state of Michoacan said. Silvano Aureoles said on Twitter that the operation took place near the violent city of Apatzingan, in Michoacan, and was aimed at detaining "leaders of criminal cells". It was not immediately clear which gang was responsible. "During the operation, an official helicopter whic…