[JURIST] Chief Judge John M. Roll of the US District Court for the District of Arizona [official website] was shot and killed when a gunman opened fire [press release] at a public constituent event held outside of a shopping center in Tucson on Saturday. The gunman additionally killed 5 others, including a 9-year-old girl, and wounded 20. Before serving in the Arizona District Court, Roll was a state judge and an assistant US attorney. Roll was named to the District…