Asperger's is a mild form of autism often characterized by social awkwardness.
A law enforcement official says Adam Lanza had been diagnosed with Asperger's. The official spoke on condition of anonymity because the person was not authorized to discuss the unfolding investigation.
Columbus, Ohio, psychologist Eric Butter says research suggests people with autism have a higher rate of aggressive behavior than the general population. He says this includes outbursts, shoving or angry shouting, but typically does not include planned, intentional violence.
High school classmates say Lanza was bright but painfully shy, anxious and a loner. Butter says those characteristics are consistent with Asperger's.