Authorities in one of the city's 16 districts are offering a new computer, out of 150 donated by a charitable foundation, for each gun handed in. People often have a gun at home, which could perhaps be for self-defense, but sadly it becomes a family tragedy when it is not used properly. Shootings are a daily occurrence in Mexico City, a sprawling megalopolis of 18 million people where muggings, carjackings and kidnappings are common. The computers-for-guns program, which echoes past schemes in other city districts that offered groceries for guns, will target some of the district's most crime-hit areas.