What if police believe a false statement?

Me and my boyfriend walked into a friends house which is a local hangout. There were 3 people in there already that we fairly knew and were just hanging out. We didnt think much of it. The owner was in the backroom with his gf. Well we were all just hanging out around a table and one of the three people blindsided my boyfriend and basically gave him a good beating for no reason. Apparently he was talking "****". Then they robbed a person there and took marijuana and money. I had no clue there was marijuana. Me and my bf had to go to the er and are trying to press charges. I gave my statement...it was very clear even with a diagram of where everyone was. Well now the people who beat my boyfriend are say that he was selling and gave him a weak bag and that my bf swung first. This is a completley false story....none of that happened and the police seem to be leaning on their side? what do we do?!