The U.S. has identified the mastermind of the Benghazi attack, sources tell Fox News, though the individual apparently is walking free in Libya.

The confirmation from multiple sources comes more than seven months after the assault on two U.S. locations in Benghazi, Libya, where four Americans -- including Ambassador Chris Stevens -- were killed. President Obama pledged after the attack that "justice will be done."

But one source told Fox News the government is "sitting on" information.

"We basically don't want to upset anybody, and the problem is, if Ambassador Stevens' family knew that we were sitting on information about the people who killed their son, their brother, on and on, then, and we could look them as a government in the face, then we're messing up. We're messing up," the source said.

Fox News spoke exclusively with one special operator who watched the events unfold in real time and has debriefed those who were part of the response. He remains anonymous for his safety and has decided to talk because he says he and others connected with the Sept. 11, 2012, attacks in Benghazi are frustrated with the excuses and lack of a military response since Stevens and three other Americans were killed.

"We have all the capability, all the training, all the capacity, to kill and capture not only terrorists involved, with the specific events of 9/11, and Ambassador Stevens' death, but terrorists that are feeding other regions including Europe that could eventually affect our national security in the short term," the source said. "And we're not talking midterm or long-term, this is the short-term."

The source said "it's a daily frustration."

Another threat is a larger terrorist haven that continues to build in parts of Libya and North Africa. Those working the region in the interest of U.S. security say the ball is being dropped by top leaders at the White House, Pentagon and State Department.

"Benghazi, the second-highest population of foreign fighters, and the war in Iraq came from Benghazi, second to Saudi Arabia, so we are talking about a historic location and region that has fed foreign fighters to kill Americans, and kill other coalition forces," one source said.

"The analysts, the intelligence experts all say the same thing, that if we just ignore the situation as it presents itself, eventually it will be another invasion will have to take place for us to eventually turn the tide."

He says the region also remains a weapons hub after the overthrow of former leader Muammar Qaddafi in 2011, which saw massive stockpiles of weapons in Libya move freely across the Mediterranean and in many cases into Syria. While the U.S. has claimed a more active role to find and remove an estimated 20,000 shoulder-launched missiles called MANPADS, some Americans working the area say they aren't allowed to take or even destroy the missiles because they have not been given the authority from their chain of command.

"I have come across SA-7's in the hands of friendly forces, meaning whether they are surrogate military or police forces that wanted to hand over and they were unable to do that because there was no program in place," one source said. "No government organizations were interested, no special operations organizations were interested."

Asked if it was frustrating to know that those on the ground are willing to pass along weapons, yet without a plan in place for the transaction, the source said: "It was frustrating not only for myself, but for the men and the guys that I work with. We always talk amongst each other and discuss it's probably going to take a 747, a 757 to get shot down in Tripoli for somebody to pay attention to that, which is unfortunate."