(CNSNews.com) - Syria has become a matter of homeland security, and we're very concerned about Syria foreign fighters, people who are going into Syria, being recruited by extremists there," Homeland Security Secretary Jeh Johnson said in an interview that aired Sunday on ABC's "This Week."
Johnson, worried that fighters trained in Syria could travel to Europe and even the United States, said the U.S. is "working together" with European governments to share information that could help track potential terrorists returning from Syria.
Asked if some of those individuals have been in the U.S., Johnson said, "We are continually monitoring the situation, and we are concerned, yes."
(Rep. Michael McCaul (R-Texas), chairman of the House Homeland Security Committee, also has identified Syria as the "largest and most significant threat" to U.S. security.)
Johnson said other terrorist threats include Al-Qaeda in the Arabian Peninsula; and the "lone wolf, the independent actor," such as those who set off bombs at the Boston Marathon.
Johnson said he also worries about ongoing cyber attacks; and mass shootings in the United States:
"This is a growing phenomenon around the country," he said, speaking of mass shootings. "It's Army bases. It's Navy installations. It's schools. One of my own people, TSA Officer Hernandez, was killed at LAX last fall."
Asked how he intends to deal with such incidents, Johnson was vague:
"I think we need to do more. I want solutions before I leave office," he said.