Chambliss: Boston bombers "our worst fear"

As investigators try to determine what shaped the alleged Boston Marathon bombers' views and motivations, Sen. Saxby Chambliss, R-Ga., said Sunday on "Face the Nation" that it appears "this was our worst fear, and that is, a home-grown terrorist, or a terrorist that was sent here to be ingrained within the community."

Suspects Dzhohkar Tsarnaev and his now-dead brother Tamerlan lived in the United States for years, and investigators believe they were influenced by the online preachings of Islamic radicals.

"These guys, they flew under the radar," Chambliss said.

Sen. Claire McCaskill, D-Mo., noted "there is no evidence at this point that these two were part of a larger organization, that they were, in fact, a part of some kind of terror cell or any kind of direction. It appears, at this point, base on the evidence, that it's the two of them."

CBS News' John Miller said that the suspects' influences represent part of "a shift in paradigm, which is basically the idea that it's not al Qaeda as much as it's al Qaeda-ism."

There are a number of potential influences, including the suspects' mother, Miller said. The Russians told the U.S. government it had concerns about Tamerlan Tsarnaev and his mother in 2011, and the FBI conducted a limited inquiry and closed the case in June 2011.

While there's no evidence the suspects were part of a larger organization, CBS News' Bob Orr noted the bombs used were somewhat sophisticated.

"If they used remote triggers -- which seems to be the consensus -- it's hard to imagine two guys under the radar could buy all this stuff, build these bombs, carry off the attack and have it all work perfectly," he said. "Where did they practice? And that begs the question did anybody help them train."

Sen. Lindsey Graham, R-S.C., said "information sharing failed" in this case. When the FBI investigated Tamerlan Tsarnaev in 2011, he said, they should have alerted Boston officials. When he went back to Russia in 2012, the Department of Homeland Security should have alerted the FBI. Furthermore, officials should have noted the extremist YouTube videos Tsarnaev started publishing online.

"So it's a failure to share information and missing obvious warning signs," he said. "We're going back to the pre-9/11 stovepiping."