Counting only the incidents with at least two casualties, there were 179 such crimes between 1966 and 2010. In the 1980s, there were 18. In the 1990s, there were 54. In the 2000s, there were 87.
If you count only such crimes in which five or more victims were killed, there were six in the 1980s and 19 in the 2000s.
Why the increase? It cannot be because gun-control laws have become more lax…gun controls today are far stricter than at the time when “active shooters” were rare.
Entire piece by David Kopel in the Wall Street Journal worth reading.