@bitter. 
You can shoot as many times as you want with any action, including muzzle loaders.
As Kursk says, all semi automatic means is that every time you pull the trigger the gun will fire untill ammunition is depleted. They are also referred to as self loading. It's a trigger function, nothing more.
Some Nerf guns are semi automatic. As are some BB guns and quite a few lower powered air rifles. It has next to nothing to do with lethality of a gun.
Semi automatics are available in the UK, Australia, and pretty much every country. They don't have school shootings.
There is no correlation between a countries citizens having access to semi automatics and death's of 1000's.
You can be very nearly as quick as a semi automatic with an under lever action, MARS and leaver release actions (watch the biathlon at the winter Olympics, their guns tend to be level release, and see how quickly you can shoot one of those...). None of which are technically semi automatic.
What other countries (including this one) recognise is that people should probably be checked out properly before they get any sort of gun. That is not a crazy idea.