A teenage gunman has killed 19 children and two adults at an elementary school in South Texas, the deadliest school shooting in nearly a decade.
Four students were killed and seven others were injured in a shooting by a teenager at a high school in Oxford, north of Detroit.
A 17-year-old student at his high school outside Houston, Texas, killed nine students and a teacher before surrendering to authorities.
A former student at Marjorie Stoneman Douglas High School in Parkland, Florida, murdered 17 students and teachers.
A gunman chased and opened fire on an Oregon college campus, killing nine people before police killed him.
A heavily armed gunman killed 26 people, including 20 children aged five to 10, at Sandy Hook Elementary School in Connecticut.