Investigators still have much to learn about the bomb blasts at the Boston Marathon on Monday, even after releasing the identities of two young Chechen suspects.
Dzhokhar A. Tsarnaev, 19, remains on the run as of Friday afternoon. His 26-year-old brother Tamerlan died in a police shootout in the early hours of Friday morning.
Security experts agree their recent travel patterns will yield a great deal of information about why two young Chechen immigrants would want to attack a high-profile American target.
"That surprised me a bit," says Rudy DeLeon, who served as deputy defense secretary under Donald Rumsfeld and William Cohen. Most attacks involving Chechen extremists have been aimed at Moscow or other Russian points of interest.
There has never been a Chechen attack on U.S. soil, and no documented attacks on U.S. interests abroad.
"You would almost be ready to put them in the lone wolf category," DeLeon says. "But one of the things we know is the first reports are usually wrong."
DeLeon, now a senior vice president at the Center for American Progress, highlights a common element to high-profile attacks like this but also one that has particularly dogged this bombing. Media outlets desperate for information have on multiple occasions published or broadcast supposed facts that turned out to be incorrect, such as news of an arrest on Wednesday, or that there was a third bomb at the JFK Library. This follows reports after Sept. 11, 2001, of additional car bombs following the plane crashes. Those loud noises turned out to be American military jets racing to intercept passenger planes still in the air.
"What's significant is that we are now fully meshed in this digital age. From the images of the department store to the YouTube and Facebook accounts, we have more hard information that we've had ever," DeLeon says. "But the model that the first reports are wrong, that continues."
The most important next step for law enforcement will be to capture the younger Tsarnaev brother before he puts himself in a situation where he might get killed.
"He has it all," says a retired Diplomatic Security special agent familiar with counter-terrorism investigations who spoke with U.S. News. "He's the only one who knows if there are any other connections, when this all started."
These are only the first questions that the 19-year-old could answer, as well as whether he participated from the beginning or if his older brother dragged him into it.
"There's a lot that has to be done still, and it's imperative that this guy be captured alive," he says.
Initial reports indicate the younger Tsarnaev was eager to escape the bloody shootout that killed his brother. Some even indicate that he ran his brother over while trying to escape. This would indicate that he is not a dyed-in-the-wool extremist who is willing to die for a cause.
"To me, that indicates that the younger brother has no intentions of going down in a blaze of gunshots, or it would have happened right there," the source says.