Neurologist Dr. Oliver Sacks speaks at Columbia University in June 2009 in New York City. Sacks, a prolific author and commentator, has died at age 82. Chris McGrath/Getty Images hide caption

itoggle caption Chris McGrath/Getty Images

People attend a candlelight vigil in front of the WDBJ-TV station in Roanoke, Va. a day after reporter Alison Parker and cameraman Adam Ward from the station were killed during a live broadcast. Don Petersen/AP hide caption

itoggle caption Don Petersen/AP