Back before my knees and elbows turned into mush, I used to practice jiu jitsu. I was very middling, but it was rare I wasn't the best wrestler in the room, so the MMA guys would often seek me out to spar. I'd show them a technique or two, and they would reciprocate with striking and choking tips. Fun stuff...but some of them were pretty clearly just insane.
One of insane guys I rolled with made it as far as Strikeforce, and had some wins over UFC vets. Lumumba had a very sad post-fight-career story before this week, but it just got sadder.
https://mmajunkie.usatoday.com/2024/08/lumumba-sayers-arrest-murder-childs-birthday-party