London investigators grapple with unprecedented, gruesome terror tactics

(CBS News) New details have emerged regarding the background and tactics allegedly used by the two men accused of savagely murdering British soldier Lee Rigby in London on Wednesday.

According to British media reports, Michael Adebolajo, 28, was a British citizen, born in Nigeria, raised as a Christian, and is believed to have converted to Islam over the course of the last decade.

He and 22-year-old Michael Adebowale were both reportedly known to British intelligence officials, but were not considered high-risk -- a potential oversight that parallels the Boston Marathon bombing. Two years before the attack occurred, U.S. officials were alerted by Russian authorities about a potential terrorist threat connected to now-deceased Boston bombing suspect Tamerlan Tsarnaev.

CBS News senior correspondent John Miller, a former assistant director at the FBI, says British authorities are now grappling with questions similar to those raised in the U.S. intelligence community by the Boston Marathon Bombing-- ostensibly, is it a case of self-radicalization or so-called homegrown terror? And, Miller asks, "Are they part of a cell or are they on their own? If they're part of a cell, is that part of a network?"

Miller says British police conducted searches of the suspects' residences on Thursday in their attempt to answer those questions. He added that, according to sources consulted Thursday, neither of the men is believed to have travelled to the United States.

The attack represents new challenges for British authorities, says Miller.

"We've never seen anything like this before in this combination. First you have your terrorist attack, the running down with the car and the assault and then the butchering of a soldier in the street, as a public event, as a spectacle.

"Then, you have the spontaneous communique -- not a video released to YouTube -- him saying it right to people on-camera at the scene, issuing the statement," he added, noting one suspect's videotaped diatribe in the moments after the attack.

"Then, you have a very odd combination... they've set up the body of the soldier as what we call a 'come-on.' It's something that we know the police are going to respond to and they wait there and once the police come, one of these guys charges with the knife, tries to martyr himself... the other individual is now... trying to shoot at the police...We've never seen anything quite like that before."

Looking ahead, British investigators will likely have to address two red flags raised by the London attack. First, the time lag -- approximately 14 minutes -- before an armed police squad arrived on the scene. 

And secondly, they will reevaluate what they might have missed when the two suspects were probed in past investigations. According to Miller, the road ahead for London investigators is "the same thing the FBI is going through in the Boston case."