Before the bombing at the Boston Marathon, a common image in the United States of a terrorist was of a crazed individual, most likely a psychopath -- certainly not someone who, like Dzhokhar Tsarnaev, liked hanging out with friends and was described as "jovial" and "a normal American kid."
Now that the country has seen the terror a seemingly "normal" person can invoke, many experts are encouraging communities to help with the counter-terrorism effort: Parents, friends, teachers, coaches can be instrumental in preventing outrageous acts, they say.
If the public were as aware of what makes terrorists tick as they are about underage drinking and drugs, acts of terrorism could be prevented, experts said. Griffin outlines a common scenario of how people get caught up in violent plans:
"Terrorists become terrorists from being normal, mixed-up people," says Roger Griffin, a professor at Oxford Brookes University in England and author of Terrorist's Creed. Fanatical Violence and the Human Need for Meaning. "Parents and faith leaders (could help if they) were more aware of the fact that they could have in their midst someone who seems quite well-integrated, but is actually hiding what they really feel is their 'sacred mission'."
A depressed person focuses his dissatisfaction on one particular cause, whether it be animal rights, abortion or religion. They start becoming isolated as they hone in on that cause, and eventually their worldview gets split in two: good and evil.
"They're part of the good and they have a mission," Griffin says. "In their mind, they become a warrior in a secret war. They choose a symbolic target, and they've got this narrative going in their head and lets them believe that if they do this terrible thing, something magic will come of it."
As that narrative increasingly takes over their lives, they become adept at hiding things.
It's an extreme and rare state of mind, he says, but common enough that it follows a pattern. If friends or family members are able to notice that pattern, it's possible to break it.
"These people are giving out signals, but they're going to be misread or ignored if we have this view of a terrorist as a wild-eyed Jihadist," Griffin says.
The signs can be subtle, Griffin admits, and you probably don't want to phone the FBI every time someone's behavior changes. But taking them to someone such as a therapist or respected teacher might help tease out what's going on.
Phillip Lyons, executive director for the Center for Policing Innovation and a professor at Sam Houston State University, agrees.
"A lot of times, with 20/20 hindsight, people knew there was something suspicious," he says. "So the recommendation we would give ordinary folks is, if something looks out of the ordinary, if something is raising red flags for you, report it. If it turns out to be nothing, no harm, no foul."
For example, a few people knew that one of the 9/11 terrorists was taking flying lessons to learn how to take off but not land, Lyons says. In hindsight, that detail could have been invaluable to authorities.
Many think that community policing is more important now than ever, he says, and he's seen it work: Some mosques, he says, have notified the police when members seemed to be in the process of being radicalized. But they only do that if they trust the police, which, in turn, happens when the police understand all the people in their communities.
Although the signs that somebody is being radicalized are subtle, they may include anger, often against the government or American society, spending a lot of time online, spending time in groups of people who are similarly angry, and inexplicably losing interest in things they had been interested in before, Lyons said.
"If you're looking for psychos all the time, you'll miss them," Griffin says.