My 17 year old Brother got beat up by a 19 yo about a month ago, he was swollen in the face at the time and?

has been showing signs of retina detachment. I have taken him to an optometrist but he saw no signs of detachment physically but my brother is seeing flashes in his vision. I have yet to file a police report but I want to now because I want that 19 yo to be responsible for any medical bills related to this malicious incident. On top of it all I didn't take pictures of his injury and I learned the 19 yo's parent was supplying alcohol to both my brother and other minors which fueled the 19 yo's rage on my brother. I am unsure of what to do? I would like to make a police report by monday so I have it filed if I pursue any sort of legal activity against the 19yo and his mother. How should I go about this? Any help would be greatly appreciated.