Vaporizer pens look like the e-cigarettes that dispense nicotine. But these devices are optimized for a potent marijuana resin with high concentrations of THC. Courtesy of Grenco Science hide caption

itoggle caption Courtesy of Grenco Science

Chris Kyle, retired Navy SEAL and bestselling author of the book American Sniper: The Autobiography of the Most Lethal Sniper in U.S. Military History, in April 2012. He was killed Saturday. Paul Moseley/Fort Worth Star-Telegram /MCT /Landov hide caption

itoggle caption Paul Moseley/Fort Worth Star-Telegram /MCT /Landov