No one has the right to deprive others of their lives.
If the thief was killed by a Tibetan mastiff when no one came to your house to steal, the responsibility might be lighter. If the thief forced his way into the darkness and stole it for robbery, and threatened the owner's life, you set the Tibetan mastiff free in self-defense. If you are killed and suspected of excessive defense, you should also bear certain responsibilities.
No one has the right to deprive others of their lives, including thieves. Only the state has the right to deal with criminals who commit heinous crimes. Illegally depriving others of their lives, for whatever reason, is unavoidable, which is essentially different from self-defense.
Now the only way for you to reduce your responsibility is to refuse to admit that you saw the Tibetan mastiff kill the thief. Say it in such a big way, that is, deliberately let the Tibetan mastiff bite him to death. It is recommended to consult a lawyer to prepare. Using Tibetan mastiff can't offset your responsibility.
Whether the dog owner needs to bear civil liability depends on whether the dog owner is at fault.
1, whether to apply for a "dog license", that is, a "dog license". In fact, whether it is urban or rural, famous dogs or local dogs, you have to apply for a certificate if you want to raise them. It is compulsory in some cities, but it is not compulsory to apply for a license in some places. However, applying for a license has the legitimacy of "keeping a dog" and can avoid some legal problems. Although there is no problem in not applying for a permit, if there is a legal problem, you will have no legitimacy.
2. Whether compliance management obligations are fulfilled. Dogs can't be kept in open places, including their own easy-to-access courtyards.
3. Whether the dog owner is present. If you have a "dog license", the dog owner is not at the scene, the dog is locked in the house, and the dog sneaked into the house and was killed by the dog. The dog owner does not have to bear civil liability for compensation. Because all aspects are legal and there is no fault. However, if any of the above three items cannot be achieved, the dog owner will be liable for compensation.
I don't care about responsibility.
Another possibility is that you let the Tibetan mastiff bite the thief, because the thief came to your house to steal. If that's the case, you're directly killing people on purpose.
Why do you say that? The thief went to your house to steal, but in any case, he didn't deserve to die. But your Tibetan mastiff killed the thief. As the owner of the Tibetan mastiff, you did not stop it in time, but watched the Tibetan mastiff kill the thief.
Yes, you don't care. On the other hand, you are an accomplice on purpose. In this way, you are not only responsible, but also mainly responsible, even criminally responsible! To some extent, your heart is more cruel than Tibetan mastiff. You can watch the Tibetan mastiff kill the thief on the spot, but turn a blind eye. Thieves are immoral, but you are cruel enough, and you will go to jail!