What does 2 Samuel 4:12 mean?

So David ordered his men to kill Rechab and Baanah. They did, then cut off their hands and feet and hung their bodies by the pool in Hebron. But they buried Ish-bosheth's head in Abner's tomb at Hebron. 2 Samuel 4:12 - Modern Text Bible

(David has the brothers executed and their bodies displayed as a warning. He treats Ish-bosheth's remains with respect, burying his head properly.)