Security experts fear that al Qaeda or a U.S. born "lone wolf" may try to strike back at the U.S. for the death of Osama bin Laden and in a sign of the urgency, an elite unit of Marines who handle chemical and biological weapons attacks was recalled today from Japan.
The death of the world's most wanted terrorist has security experts at all levels of government concerned that bin Laden's loyal and fanatical followers could launch a series of deadly attacks.
"Though bin Laden is dead, al Qaeda is not," said CIA Director Leon Panetta. "The terrorists almost certainly will attempt to avenge him, and we must—and will—remain vigilant and resolute. But we have struck a heavy blow against the enemy."
Sen. Joe Lieberman, chairman of the Senate's Homeland Security Committee, feared the attack could come from a source other than al Qaeda.