School Shooter Laurie Dann in Bloomington, MN

In 1988, a small suburban town in Illinois mourned the murder of an eight-year-old boy who was shot to death in his classroom. The shooter's rampage left five people in critical condition, though they would eventually recover. The most regrettable part of the whole ordeal was that the shootings could have been prevented if police paid closer attention to warning signs displayed by Laurie Dann. In the end, she decided to take her own life rather than face retribution from her victims' families.