他是个精神变态杀人者。He's a psychopath, a killer.杀人者处死刑.The punishment for murder is death.留在枪上的指纹证实他就是杀人者.The identity of the fingerprints on the gun proved that he was the killer....

“杀人者”的英语可以翻译为：[医] homicide，manslayer，murderer ...