那个罪犯被确认为大规模谋杀犯。

The criminal was identified as a mass ___murderer.

几周后，警察抓到了我最好朋友的谋杀犯。

A few weeks later the police caught the ___murderer of my best friend.

那个谋杀犯承认了罪行。

The ___murderer confessed to the crime.