Police stepped up armed patrols in south London Thursday after the month’s third fatal shooting of a neighborhood teenager gave rise to mounting concern about gun crime, despite statistics that showed many such crimes dropping. Billy Cox, 15, was shot dead in a public housing complex on Wednesday. On Feb. 6, 15-year-old Michael Dosunmu was gunned down in his bedroom, three days after James Andre Smartt-Ford, 16, was killed by a gunman at an ice rink in the city. Full Story