Is there any punishment for a Muslim that kills an innocent?

[Nitro Zeus]

‎السلام عليكم‬

Long ago on Quora website, I've been arguing with an American non Muslim user about punishment for a Muslim that kills a non Muslim. I told him that if a Muslim kills a non Muslim, then that Muslim is regarded as a murderer and he is sentenced to death as his punishment under Islamic law and he insisted with his ideology that there is no punishment for a Muslim that kills a non Muslim.

I tried to research myself on Internet about this, but I did not had any luck in that.

Could you please tell me if there is a capital punishment for a Muslim that kills an innocent non Muslim? If yes, could you please quote for me strong and authentic evidence from Quran and Sunnah?

 

['Abdullah]

Quran says:​

….whoever kills a soul unless for a soul or for corruption [done] in the land - it is as if he had slain mankind entirely...(Quran 5:32)

So killing of anyone (Muslim or non-Muslim) is a major sin with the exceptions mentioned in above quoted verse.
Islam is a religion of peace and throughout history non-Muslims have lived in peace and harmony under Muslim rule. Muslims ruled India for about a thousand years, and therefore had the power to force each and every non-Muslim of India to convert to Islam or to kill them, but they did not because it is against Islamic teachings. Thus more than 80% of the Indian population remain non-Muslim even after living under Muslim rule. This is a historical fact and clear proof of Islamic teachings of tolerance and respect to other religions.
Below is a very good article which has more evidence from Quran and Sunnah on this subject and hope you will find that helpful to make your case.
https://www.islamreligion.com/articles/391/rights-of-non-muslims-in-islam-part-10/
This website has more than 23 articles on rights of non-Muslims in Islam. And hope your friend will read these with an open mind. If he does then it will be good for him, if he does not then there is no need to argue. Your job is only to convey the message with respect.
https://www.islamreligion.com/category/85/islam-and-non-muslims/
Ma'a Salama