Hi, I have a 2 year old Beagle/lab cross and today he bit my 9 year old son. My son let the dog out into the garden to do its business and opened it again to let him back in. As my son closed the door after the dog had walked back in he caught its tail in the door and the dog bit at my sons thigh. It didnt draw blood or pierce the skin but left 3 nasty little bruises. Is this nornal behaviour for a dog? How should I have delt with the matter? Thanks in advance.