I am pretty familiar with the situation since I have lived in the same county as Columbine as long as the Columbine killers parents have, and I have raised two children there. It was a "perfect storm" situation where stress, parental neglect, a wasteland Suburbia, video game/tv/internet culture, and gifted minds gone awry came together.
Across the street from my children's school is a maximum security prison. The Unabomber spent time there, and Timothy McVeigh. Both men were probably gifted, like Eric Harris was.
If we "removed all the evil people from society" then there would be nobody left. In the US, we already incarcerate more people than in any other developed nation! I would probably be behind bars, since a person just called me "evil" recently, when I got out my Tarot deck to do a reading.