It's bad to harm other people's pets.
Alfred was second in line behind his master's dog to inherit all of the master's money, who recently passed.
Alfred wants to obtain the money.
Alfred waits for the old dog to simply pass on it's own and continues his work.
Alfred poisons the dog in order to hasten his inheritance money.
Sure enough the dog passes away a few months later and Alfred gets the money.
Alfred is not caught, but people think it suspicious the dog died so soon after it's owner.