I always strive for a humane shot. As long as you shoot them in the brain or chest they are going down. I take the shot that is given me. Sometimes a head shot does not present itself. In that case I go for the chest shot into the heart/lung area. Some people are put off by flopping around of a brain shot squirrel. Provided it was a well placed shot to the brain, it is instantly killed and the flopping is only the nerves. Always follow up with a quick kill shot if a squirrel is wounded.