Mosque killings (or any killing of innocent people) are surely despicable acts but incidents such as this where a lone gunman runs amok, I have only seen happen in America, Ireland (Dunblane school massacre) etc. more recently that Norwegian nutcase (Anders Breivik) who donned a police officer’s uniform to trick people before massacring 67 Norwegians on Utoya island.
And you have to say that school shootings are far more frequent in America than in other countries, although terrible massacres have occurred in Russia, Israel, and several European nations.
In London there are many stabbing incidents involving teenagers, something that doesn’t happen in most other countries