Charles Whitman kills 16 people shooting a rifle from the tower on the campus of the University of Texas on August 1st, 1966. He was shot and killed by police.
Teenagers Eric Harris and Dylan Klebold use guns and homemade bombs to kill 12 students, one teacher, and themselves on April 20th, 1999.
17-year-old Jeffrey Weise kills nine people, including his grandfather, before killing himself on March 21st, 2005
32-year-old Charles Carl Roberts kills five girls execution-style inside a one-room Amish schoolhouse in Nickel Mines, Pennsylvania on October 2nd, 2006 before killing himself.
National Guard troops kill four students participating in anti-war protests on campus on May 4th, 1970.