Can this be a case with the German Polizei?

We closed the phone with my boyfriend around midnight and he was about to arrive home 1-2 minutes later, 1 hour later when I didn't hear anything(text, good night etc.) from him, I called and for 3-5 calls I couldn't reach him, which is hardly a case. Then he responded me with sms that he was in police station and later he will talk. 10 mins later he called me and told me, in front of one of the high floor buildings(not the safest environment in Berlin recent years) he saw a fight between two 20s year old men and he tried to separate them without getting much involved because he thought they were going to kill each other. He mentioned no tools weapons etc. 1 min later police comes to take them to the police station along my boyfriend, when my boyfriend didn't want to come with the police vehicle because he should come back himself, they let him come with his car but taking his phone and ID card with them. This is the point I am surprised, if you are not even involved, can police take your phone and Ausweis? If you are involved, do they let you with the car? At police station he waited around 1 hour to testimony and without any document/report or sth they let him go later on. I'm not in my 20s, embarrassed to not to believe my boyfriend's story, but something sounds weird here,is it even possible?