In 1996 a lone gunman entered a classroom in Dunblane, Scotland.
David Barnes

And the same thing happened after the Dunblane inspired massacre at Port Arthur in Australia in 1996.

The Australian government enacted stricter gun laws and there have been 3 shooting sprees since. That’s 3 in 19 years. Only one of them was someone randomly shooting people (In 2002, 6 years after Port Arthur), the other two seem to have been a domestic dispute and a row between neighbors that got out of hand.