The FBI has helped to disrupt or prevent nearly 150 shootings and violent attacks this year, in part by steering potential gunmen toward mental health professionals. There have been hundreds of these disruptions since 2011, Attorney General Eric Holder told an audience of police chiefs in October, touting the behind-the-scenes work of a small FBI unit based out of Quantico, Va. In most cases, the FBI has helped potential offenders get access to mental health care.