What does 2 Samuel 18:14 mean?

Joab said, 'I'm not going to waste time with you.' He grabbed three spears and drove them into Absalom's chest while he was still alive, hanging in the tree. 2 Samuel 18:14 - Modern Text Bible

(Joab takes matters into his own hands, killing Absalom himself. He acts quickly and decisively, ignoring David's wishes.)