We investigated a single complaint, but then it came out that he had similar behaviors towards a few others in the past and in the interim.
What he did was a number of things. He befriended the kid acting as an unofficial "coach". He would go to the ice rink stick and puck sessions and teach the young players some stickhandling (pun not intended) and even get them to refer to him as "coach". (He was not a coach) He would then direct additional attention to a few. The one we investigated, he gave the kid (12 years old) an electronic device with porn loaded on it and saved porn web-links. He told the boy "do not tell your parents". He then used the device to message him late at night and they messaged about rating the videos. Then he started to drive him home from school (without the parents knowing). He met up with him away from the rink on a few occasions too, and provided him with gifts. He was using the fake persona of "coach" to gain trust, and even some of the parents of these kids helped enable him by encouraging him. These parents were quite vocal and protective of this guy as we ran through our process as they had been duped and had no idea (and still actually have no idea). We could not share our evidence, so these parents made out the board of the club to be the bad guys.
We hired an attorney specialising in family law to advise us. It is quite scary at how little you can actually do until someone really gets hurt. We expelled him from the sports club for serious misconduct, but we were unsuccessful at getting him trespassed from the rink. I still see him there at the public sessions "coaching".
He appealed the expulsion, and had one of the duped parents sit in at the hearing as his "support person". The new evidence for us to consider was a letter from the police stating that he had not been charged with any crime. We already knew that and had considered in the first instance. This did give us the opportunity to ensure that someone else saw this evidence and this parent was ghost-white when he saw what was on this device. His kid was hanging out with the guy prior to that. The parent was pretty quiet on this front thereafter.
Had the parents of this 12 year old not found this device and brought this to our attention, I feel pretty confident that something really bad would have happened there. That's all. Sounds like your training session does suck. As an ED doc, I'm sure you see the after effects of stuff like this all too frequently and would never minimise it.