In 2010, Omar Thornton killed eight colleagues in Manchester, Conn., before killing himself. Private employers used to create their own rules about guns on their property. But over the past five years, many states have adopted laws that allow employees to keep firearms in their vehicles at work. Douglas Healey/Getty Images hide caption

itoggle caption Douglas Healey/Getty Images

As the mayor of Cali, Colombia, epidemiologist Rodrigo Guerrero (left) meets with the police once a week to review murder statistics. Courtesy of Prensa Alcaldía de Calí hide caption

itoggle caption Courtesy of Prensa Alcaldía de Calí

Involuntary commitment to a hospital for mental illness can be a lengthy and complex process. A California law makes mandatory outpatient treatment an option. iStockphoto hide caption

itoggle caption iStockphoto

Lt. Gen. Mark Milley speaks to reporters April 2 regarding the second shooting in five years on the Fort Hood Army post in Texas. Drew Anthony Smith/Getty Images hide caption

itoggle caption Drew Anthony Smith/Getty Images

An ambulance makes its way through revelers in Cardiff city center in Wales in 2010. New measures in the city have reduced injuries caused by violence. Matt Cardy/Getty Images hide caption

itoggle caption Matt Cardy/Getty Images

Somali women and children wait to get medicine in July 2008, from a clinic run by Doctors Without Borders about 20 miles south of Mogadishu. AFP/AFP/Getty Images hide caption

itoggle caption AFP/AFP/Getty Images

A police officer guards Cambodia's famed temple of Angkor Wat. The powerful city-state collapsed in 1431 after suffering through two decades of droughts. Heng Sinith/AP hide caption

itoggle caption Heng Sinith/AP