'Shedding' in the Bible

When Abner returned to Hebron, Joab brought him aside within the gateway to talk to him alone and then stabbed him in the abdomen. So he died for shedding the blood of Joab's brother Asahel.

How much worse will it be, then, when evil men kill an innocent man on his own bed in his own house! Shouldn't I avenge his blood which you are responsible for shedding by removing you from the earth?"