I have a Jack Russell that recently turned one. He has always been sweet and lovable until this morning. He seems like a totally different dog, and has many strange behaviors today. This morning as usual he was sitting in my lap and I was petting him when all of a sudden he tried to bite me, then he jumped down and ran under the bed. He bit my granddaughters finger, and just started growling at my brother. He normally sticks right by me but today he is staying under the bed. What is going on?