David Bowdich, center, assistant director of the FBI's Los Angeles office, talks to reporters during a news conference on Friday, Dec. 4, 2015, in San Bernardino, Calif. The FBI said Friday it is officially investigating the mass shooting in California as an act of terrorism, while a U.S. law enforcement official said the woman who carried out the attack with her husband had pledged allegiance to the Islamic State group and its leader on Facebook.
David Bowdich, center, assistant director of the FBI's Los Angeles office, talks to reporters during a news conference on Friday, Dec. 4, 2015, in San Bernardino, Calif. The FBI said Friday it is officially investigating the mass shooting in California as an act of terrorism, while a U.S. law enforcement official said the woman who carried out the attack with her husband had pledged allegiance to the Islamic State group and its leader on Facebook. Jae C. Hong AP
David Bowdich, center, assistant director of the FBI's Los Angeles office, talks to reporters during a news conference on Friday, Dec. 4, 2015, in San Bernardino, Calif. The FBI said Friday it is officially investigating the mass shooting in California as an act of terrorism, while a U.S. law enforcement official said the woman who carried out the attack with her husband had pledged allegiance to the Islamic State group and its leader on Facebook. Jae C. Hong AP

David Brooks: How the Islamic State makes radicals

December 10, 2015 12:00 AM