Today marks the 10-year anniversary of the Sandy Hook school shooting. On December 14, 2012, a gunman killed 20 students and six adults at Sandy Hook Elementary School in Newtown, Connecticut. The tragedy is one of the worst school shootings in American history. A permanent memorial was set up at the site of the school. It features a sycamore tree surrounded by a ring of water with 26 granite stones engraved with the names of those killed.