In 2012, police arrested a man named Israel Keyes in connection with the death of a barista in Alaska. But this wasn't an isolated incident in the life of Keyes; It turns out he was a serial killer who may have been responsible for at least 10 additional deaths. Maureen Callahan, author of "American Predator: The Hunt for the Most Meticulous Serial Killer of the 21st Century," thinks the number may be much higher. "He killed all over the United States," she told InsideEdition.com.