Imagine the following situation. A criminal committed a crime (for example a robbery) with several associates. Then he found out that his associates may have been investigated and arrested and they might have informed on him. So he took action and killed his associates to silence them.
Is there any idiom or collocation used for this action - for killing fellow criminals? I think it may exist because I heard in on a TV years ago but I was not able to find it.
EDIT: I found out that the detective in the show used the idiom tie up (some/a few) loose ends, which is quite general and can be used on plenty of others occasions. Answers presented below may be more suitable to the story.