If an individual is committing a crime against your property, I do not believe you have the right to kill them. In this thread a lot of people are relying on the logic that stealing your cat converter could lead to you losing your job and spiraling into homelessness.
If someone is doing something that you can reasonably interpret as trying to kill you (or assault you) then you are allowed to defend yourself. This may be shocking to people of your perspective (not a personal attack), but in Australia individuals have been sent to jail for the second punch they have thrown after the first punch had effectively reduced the risk of death or injury to 0 (eg knocked out the criminal, the criminal began fleeing). This is exactly what I am referring to when I said that we grant criminals the same humanity as everybody else. In Australia (and some countries in Europe), Criminals DO expect mercy or pity from their victims, lest the victim risk legal trouble themselves, and if you go and compare the crime rates and violent crime rates of these countries with those that do not practice this philosophy, I think you will find that our harm minimization policy works better.