noun
Refers to the act of killing or to a person who kills. As 'murderer', it is often used in compounds or set phrases like 人殺し.
彼は殺しの容疑で逮捕された。
He was arrested on suspicion of murder.
あの男は人殺しだ。
That man is a murderer.
殺人 is a more formal or legal term for homicide/murder, while 殺し is a colloquial nominalization of 殺す.
殺す is the verb 'to kill'; 殺し is its nominalized form, used as a noun meaning 'killing' or 'murderer'.
Nominalized form of the verb 殺す (ころす, 'to kill').