Last Updated 10:27 a.m. ET
(CBS News) Critics have faulted the Obama administration for changing its reporting on the consulate attack in Libya, but senior correspondent John Miller said that the focus should not be on how information was gathered in the midst of the crisis, but on what security existed in Benghazi on September 11: "What was the deteriorating security situation? How much did Washington know, and what did they deliver in terms of protection? It sounds more like they were taking it away than providing extra."
Officials tells CBS News there were repeated requests for additional security before the attack that were denied and multiple security incidents that should have served as red flags.
"What we're learning now is that there were a drumbeat of incidents, about 13 security threats," said Miller, "either directly to the consulate, a handful of those, but then incidents in the surrounding area against the British, the Red Cross and so on, and this was building up."
Among the most prominent security incidents in Benghazi were a June bomb blast that blew a hole in a perimeter wall surrounding the consulate, followed the next week by an attack on the convoy of the British ambassador, which left two security guards injured. Those have been detailed in a letter sent by Rep. Darrell Issa and Rep. Jason Chaffetz to Secretary of State Hillary Clinton. Issa is the chairman of the House Oversight Committee and Chaffetz heads that panel's Subcommittee on National Security, Homeland Defense and Foreign Operations.
CBS News has obtained a copy of a State Department email, dated May 3, 2012, responding to a request by the Embassy in Tripoli to maintain a DC-3 transport plane for security purposes. The request was turned down.
Miller said he expects a lot of news to come from next week's Congressional hearing into security at the Benghazi consulate.
"I've been to embassies all over the world and I've seen how security works," Miller said on "CBS This Morning." "When it comes to the ambassador, whether he going to make a trip, make that call, in the embassy the ambassador is king. That's going to be his call whether to go.
"But the things that go along with that - which is the security of the facility he's going to, the security provided to him on the road - a lot of those decisions aren't made there, they're made in Washington. And as we get closer to next Wednesday's Congressional oversight hearing we're going to start learning some incredible things."
Miller said one witness that may shed light on the matter is the regional security officer from Benghazi, Eric Nordstrom, "who we understand is prepared to testify about these rising security threats - and they did ask for more security in cables and memos from Washington." Another witness being sought is Charlene Lamb, the deputy assistant secretary of state for international programs, "who is the person who approves or denies those requests.
"I think we're going to see a lot of news coming out of that," Miller said.
On Thursday FBI agents and other investigators visited what's left of the consulate to document the crime scene and collect evidence. Their first visit to the scene in Libya came three weeks after the attack that killed Ambassador Chris Stevens and three other Americans.
Miller said that focus on the attack is still centering on Anshar al Sharia, a Libyan group that reads from the al Qaeda narrative.
"The question is, once they figure out the 'whodunit' part, which they're pretty close to, what do they do about that?" Miller said. "There isn't a criminal justice system in Libya that can really handle an arrest and trial, and bringing them to the United States is fraught with its own issues. They are in the decision-making process: Once we nail them down, what do we do with them?"