Not literally, of course! But a new study published in the journal Child Development suggests that neither genetics nor environment alone can be blamed for causing violent behavior in teenagers. As reported in the New York Times, the researchers found that for most teens, an early history of small behavioral problems tended to snowball into bigger issues, usually as parents pulled away from difficult children and schools washed their hands of them. Led by Dr. Kenneth Dodge at the Center for Child and Family Study at Duke University, researchers followed 750 children from preschool to high school.
What they found, in Dodge's words, confounds both typical liberal and conservative responses to teen problems. From the article:
“It’s not that they are super-predators or biologically destined to
life as a criminal,” Dr. Dodge said of the children. “It’s also not the
story the liberal folks tell: that it’s entirely a bad environment.
It’s a combination of an impulsive, temperamentally difficult child,
who elicits problems from the environment that propel the child toward
a violent adolescence."
As one of those liberal folks myself, I'd say that such a survey does confirm a few parenting philosophies on my side of the ledger. When young children have mild behavior problems, the article reports, "harsh discplinary action from parents and teachers" often made the child "more aggressive" and thwarted the development of "important social and cognitive skills."
Bottom line: for most troubled kids, a combination of nature and nurture is at the root. While we can't control our kids' nature, we can certainly aim to nurture them in a way that doesn't make things worse. 
Related: Kids fight over "your mama" joke