On Sunday, Homeland Security Secretary Jeh Johnson said a lone-wolf terrorist could "strike at any moment" in the United States.
“We’re very definitely in a new environment, because of ISIS’s effective use of social media, the Internet, which has the ability to reach into the homeland and possibly inspire others.
“Because of the use of the Internet, we could have little or no notice in advance of an independent actor attempting to strike.
“We’re very definitely in a new phase in the global terrorist threat where the so-called lone wolf could strike at any moment. Which is why the FBI, in my judgment, has done an excellent job of getting to those who are attempting to travel to Syria, who commit overt facts in furtherance of material support to terrorism. It is a new environment, but we are not discouraging Americans from doing the things that they do on a daily basis in our society," Johnson said.