I know a few people who have a license for a weapon.
But to give you an example: when a burglar enters your house, and you shoot him, you are most likely to get imprisoned for murder.
OR : if a burglar is in your house, and runs away, and you shoot him while he's already on the run, then you'll get imprisoned for sure here.
Conclusion: you may only shoot back, but never start firing yourself, even if your life is in danger, the reaction must be with equal arms....
That's the law in Belgium.