Who? How? Why? Those words began many questions last week in the wake of the Boston Marathon bombings.

From the start, speculation abounded about the type of person or persons who could carry out such an attack.

"It is a state holiday in Massachusetts called Patriots Day," said one news reporter. "Who knows if this had anything to do with these twin explosions?"

"Normally, domestic terrorist people tend to be on the far right, although that’s not a good category," said another. "Just extremists, let’s call them that. Do they advertise if they do something like this? Do they try to get credit as a group, or do they just hate America so much?"

And the speculation continued Friday after brothers Tamerlan and Dzhokhar Tsarnaev were identified as the bombing suspects.

"The Associated Press reporting brothers from Chechnya," said one news anchor. "When you hear that, what does that mean?"

"Well, unfortunately, it means Islamic fundamentalist terrorism," an analyst said.

Or does it? That’s one of many questions criminal investigative analysts at the FBI are trying to answer. You might better know them as profilers.

Former senior profiler Mary Ellen O’Toole spent half of her 28 years at the FBI with its Behavioral Analysis Unit – a unit made famous in popular culture by the likes of "The Silence of the Lambs" and the TV show "Criminal Minds."

O’Toole says, like in most crimes, many possible motives are still at play, and that there might be more to Tamerlan Tsarnaev’s turn towards radical Islam.

"They’re going to be looking for whether or not his turn toward radical, spiritual beliefs – if you took those away – was he still someone who was angry, wanted revenge, was mad at the world because things were not going his way?" O'Toole said. "And his move towards radical beliefs, political or otherwise, were not the reason that he did it, but were part of that evolution of him of having more of a personal cause for doing it. And having religious beliefs may have helped him in his own head normalize it."

Dzhokhar Tsarnaev’s personality will also be crucial to the investigation, according to O’Toole. Of particular interest will be his behavior in the days following the bombing. The 19-year-old is reported to have spent last Wednesday working out at a college gym and attending a party where one person described him as being relaxed.

"Is he a really remorseless, callous individual?" she asked. "Or as they do their background on him, are they going to find out that he is a 19-year-old man chronologically, but his emotional age is younger? We always look for emotional versus chronological age."

Remorselessness and callousness are traits that can be associated with psychopathic behavior, according to O’Toole, but she says it can also be also be a sign of immaturity that’s typical in some 18- and 19-year-olds.

O’Toole says figuring that out is important because it will help tell investigators whether the younger Tsarnaev was being controlled to an extent by his older brother, or even by someone else, if other suspects were involved.

During her FBI career, O’Toole worked on investigations into Unabomber Ted Kaczynski, Green River serial killer Gary Ridgway and the 2002 Olympics bombing in Salt Lake City. She says that while such cases, including the Marathon bombing, may share similar traits, investigators shouldn’t be quick to make a comparison.

"You can’t take things that happen very infrequently and say ‘Well, every time we see this, this is what it means,’" she said. "It will lead us down the wrong investigative path, and so every time a case like this occurs – and actually every case I ever got involved with – you have to tear that case down behavior by behavior and analyze that very unique case."

But as investigators and the public wait for Dzhokhar Tsarnaev to recover from his injuries, O’Toole cautions that whatever he might tell authorities, it will never fully close the book on last week’s events.

"When we learn what the motives are, no one will receive solace from that – no one," she said. "Because it will never justify the damage that’s been done here. So there’s a real difference between the reasons that the offender chose to do this, what was in his head – or their heads – and what we could ever hear that will reconcile what they did. There’s nothing that they will tell us that can reconcile what they did. Reconciliation and motivation are not one in the same thing."