On December 14, 2012, Adam Lanza, a 20-year-old man, entered Sandy Hook Elementary School armed and killed 26 people. 20 young children were killed along with six adults. It is one of the most tragic and painful events to occur in the United States, as it stands as the deadliest mass shooting in a high school or grade school in the U.S. The shooting also evoked a huge, nation-wide debate on gun control.

https://en.wikipedia.org/wiki/Sandy_Hook_Elementary_School_shooting