Shooters killed nine people, including a 12-year-old boy and four teens, in a blaze of gunfire at a slot-machine arcade in the central Mexican state of Michoacan, part of a wave of violence sweeping the country’s avocado heartland. Michoacan’s attorney general said in a statement late on Monday that eight people died during the arcade shootout in Uruapan, the state’s second-largest city. Authorities did not give a motive for the attack in Uruapan, a city that has long suffered from high violence as gangs vie to control production and transport of drugs such as crystal meth, and increasingly the lucrative avocado trade.