On December 14, 2012, 20-year-old Adam Lanza killed his mother at their home, then went to Sandy Hook Elementary School in Newtown, Connecticut. He killed 20 first-grade students and six staff members before killing himself.

The attack is the deadliest mass shooting at a K–12 school in U.S. history. It received national and international attention and became a focus of public debate in the United States about gun control.