Noun and する verb
じゅうさつ
犬が飼い主に銃殺されるという悲しい事件がありました。
There was a tragic incident where a dog was shot and killed by its owner.
A gun kill is a death by shooting.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.