Now that the Boston bombing suspect is in custody, we have to ask the right questions. And one of these questions is, what causes people to snap? The two killers are hardly your stereotypical terrorists. They were seemingly law-abiding citizens, one of whom became a US citizen. They were devout Muslims, but also sought to be Americans; one of them became a citizen on September 11th.
I looked back on the history of serial killing and it is not a pretty picture. The phenomenon was known in ancient Greece, where a monster was depicted as waylaying travelers, showing hospitality, and then killing them. People back then could not rely on law enforcement; therefore, the closest thing was a superhero like Theseus, who killed the monster as his first great deed. I would not be surprised if the mythical minotaur was really a person whom Minos kept underneath his palace and fed his prisoners to. The human form was central to Greek thought; man was seen as the measure of all things and the Gods were portrayed as exalted humans. I suggest that creatures like the Minotaur, who sacrificed their humanity, on the other hand, were regarded as monsters whom the gods let live as a challenge to future heroes.
Locusta was a poisoner used by the Emperor Nero to poison his political enemies in the 1st Century AD. In the Middle Ages, people were familiar with the concept of serial killers as evidenced by Guy of Gisbourne, sent by the Bishop of Hereford and the Sheriff of Notthingham to kill Robin Hood. Shakespeare was familiar with the concept as well, dressing up Richard III as a serial killer who believed that he could not help what he did because of his destiny and who would murder children and women to serve his political ends.
We all have our breaking points. Achilles became a superhero, not because of his prowess as a warrior, although he was one of the greatest warriors in Greek mythology. He became one because he came to know his breaking points and because he came to see the other side's humanity. Proper education in the schools does not mean rote knowledge through standardized testing or religious indoctrination, but self-awareness and knowing one's breaking points so that they can stay as far away from them as possible.