But people who study prisons said the number of criminals who turn to extremism behind bars is small but worrisome. And they all point to the same case to open the conversation.
"Prisoners in jail often are looking for a new alternative, and being converted to Islam, there's absolutely nothing wrong with that," King says. "In fact in many cases it's ideal for prisoners. This is the religion they've been looking for."
In fact, prison authorities say Islam, the fastest growing religion inside prison, has a positive effect on inmates' behavior. Experts who track extremism said they aren't talking about the kind of Islam that most people, including most prisoners, follow.
Mark Hamm, who teaches criminology at Indiana State University, says prisons need to make sure there are more chaplains and imams on hand to provide legitimate religious advice.