Either an intentional kill shot or a deliberate incapacitating shot. Just imagine what would happen to you if a 180 lb man tackled you from behind, full force, and you landed with your sternum on a large rock the size of two doubled up fists. People who get sucker pinched and hit their heads on curbs as they drop are often killed or permanently incapacitated.
It’s a parallel to Preston Brooks beating Charles Sumner on the floor of Congress just before the Civil War.