I'm sure glad I live in the US. In many of our states, if someone is in your home without your permission (especially as the case with these students who broke in in the first place), the owner is well within their rights to shoot them. They have to be in your home though, you can't shoot them once they're running away.
The old joke is, "If you shoot a thief who is crawling out your window, make sure you drag the body back in."
There is more to it than that, and certain very real consequences depending on the specific response used, but Judicious Use of Deadly Force is authorized for those kinds of circumstances. If that happened in America, he could simply declare them as a threat to him, and if they didn't leave after that, he could shoot them. You also have to verbally warn them before you take action (assuming there was time for that). It is part of any firearm safety course in the US.