[Yogi and mamma]

so i have been living with my mom and i have been still training him on not marking territory in the house. (hes 1 year old) so he was running around the house and he marked my moms new sofa she seen him and right when i walked in she spanked him on his butt not to hard but she spanked him he turned around and growled at her even showed his teeth. i just stood there like wow is he really growling like that? then he ran off with his ears down and ran to lay on the bed. i dont know if he was just mad or what but why would he be growling and showing his teeth like that? he is a sweet heart not a fighter?? or is it him giving her a attitude?