The shootings at Virginia Tech are the latest - and worst - in a long history of gun violence at U.S. schools and universities.
The previous most deadly incident occurred in 1966, when Charles Whitman, a university student in Austin, Texas, killed 16 people, most from a vantage point atop the college clock tower.
During the 1990s a series of shootings by schoolchildren across the country claimed the lives of classmates and teachers. The worst came in 1999, when two students at Columbine High School in Colorado killed 13 people and then committed suicide.
Late last year, three shooting incidents in one week prompted the Bush administration to hold a meeting on school safety.
In the worst of those incidents, a man shot and killed five young girls at an Amish school in Pennsylvania.
Some information for this report was provided by AFP, AP and Reuters.