Younger Brother Taken By Police For Drinking Underage (pa)

Hi, I genuinely have no idea what to do in this situation. My 15-year-old brother got into a issue after drinking a few nights ago. A friend’s mom was driving him home when he got sick in her car. She pulled over to a sidewalk and he got out and threw up. A officer pulled up, asked if he'd been drinking, then became aggressive when my brother said yes. It was stupid for him to admit to drinking but he didn’t feel well and the cop got in his face. The cop then interrogated him about pills (which he’s never taken), detained him without reading his rights, and questioned him without a parent present. He was rude to my brother’s friends mom and got loud telling her that he would be driving him home. He was also rude to my mom when he dropped my brother off. The cop’s now been harassing my brother’s friend for more info, driving by her house more than 6 times last night and calling her non-stop. He has told us that my brother is going to court and our date is in the mail, threatening with fines and juvenile detention. This situation feels so wrong and I want to know if anything this cop did is illegal. He really wants to get my brother on pills/narcotics and I feel like there is an ulterior motive. (He is also a bike cop that patrols a high-school at night, rarely does this cop patrol in a car around our small town.) I understand my brother drank underage but this wasn’t even a serious incident.