This is one of the more brutal scenes in any movie and it is well done with little splatter or gore.
Hackman is the town lawman and he just heard that hired killers will be coming to town to kill two cowboys on a contract for hire.
English Bob, is probably one of the poetntial killers for hire, and Hackman decides to send a message to all others who would try to take the contract.
This is extremely effective moviemaking.
