Adam Lanza

Adam Peter Lanza (April 22, 1992 – December 14, 2012) was an American mass murderer who perpetrated the Sandy Hook Elementary School shooting in which he murdered 20 children and six adult staff members before committing suicide as first responders arrived at the scene. Prior to the shooting, Lanza killed his mother at their home in Newtown, Connecticut. He was obsessed with previous mass murderers and studied them extensively.

Born in Exeter, New Hampshire, Lanza did not speak until he was three years old. Early evaluations found "significant delay in social-personal development" and difficulty in being understood by others. He was diagnosed in preschool with sensory processing disorder. This made light, sound, and physical touch overwhelming or painful for him. By age five, he exhibited obsessive-compulsive behaviors such as excessive hand washing and a rigid need for routine.

He attended Sandy Hook Elementary School and his challenges intensified after fourth grade. The transition to middle school—where he had to change classrooms and navigate noisy hallways—was physically and emotionally overwhelming for him. He had an Individualized Education Program (IEP) from preschool onward. However, the Office of the Child Advocate later concluded that his schools often focused on managing his symptoms rather than addressing the underlying social-emotional deficits.

As early as fifth grade, Lanza's writings involving graphic descriptions of violence, that investigators later identified as a significant red flag, went unaddressed by school officials. By middle school, his anxiety led to him being placed on homebound status, where he received instruction at home rather than attending classes. Clinicians at the Yale Child Study Center evaluated him at age 14 and recommended intensive cognitive and therapeutic support and medication for his anxiety and obsessive–compulsive disorder (OCD). His mother declined these treatments, preferring to accommodate his preferences rather than forcing him to adapt to social environments and improving his mental health.

On December 14, 2012, Lanza killed 20 students and 6 staff members at Sandy Hook Elementary School. Before arriving at the school, Lanza also fatally shot his mother, Nancy Lanza, at their home, bringing the total number of victims to 27. Two other staff members were injured but survived the attack. It remains the deadliest shooting at an elementary school in U.S. history and one of the deadliest mass shootings overall.