What are my options for getting back my possessions?

My girlfriend is trying to get her possessions back from her ex but he has changed the locks to their old house and refused to return anything. He has her dog (It is a purebred dog and her proof of ownership is in that house) along with most of her clothes, her bed and many other personal possessions. We are going to talk to the police this weekend, but are worried that there is little they can do. The long version: When my Girlfriend (A) started dating this guy (B) she lived in this house by herself. He was having trouble keeping his place and so she allowed him to move in with her. Most of the things in the house belonged to her (her dog (which she loves dearly), bed, couch, stove, washer/dryer, her clothes, furniture, dishware, etc.). Eventually they decided to break up, but with her work situation she was not going to be able to afford the rent on her own and so he said he would stay there for a while and take care of the dog and her stuff until she found a place. She was OK with this and allowed him to pretty much use whatever he needed while he was staying there, assuming she would get it back once she had a home. She has been staying with friends since then, about five months. She had contacted her ex on a few occasions to try to get some things from him and to let him know she would have her own place soon and would be ready to pick her stuff up (her and I had been looking for our own place). He began to make it clear that he wasn’t going to allow her to have anything. She went over there one day to try to get stuff and the locks on the doors had been changed. We knew we were going to have trouble getting it and so we decided we would wait until we had a place to put it all before pursuing it further. And now, after having looked for a couple of months, we have just moved into a new apartment this past weekend.