It’s undeniably scary when stuff like that happens, and you have my sympathy. In situations like this, staff training is worth its weight in gold. The trouble is that nobody really knows what to do in this kind of scenario when they are suddenly confronted with it, and can often either freeze up or make things worse. In a previous life I worked for an organisation that developed and delivered conflict resolution training for all NHS staff. It covered a range of things like the best way to recognise the signs that someone is going to become angry or even violent, how to prevent it if at all possible, talking people down from that kind of state, defusing conflict, and also practical measures like making sure you don’t find yourself with a potential threat between you and the only available exit, or within the potential reach of an assailant. Obviously in this case all of the preventative stuff is academic (unless you could argue that it could have been mitigated during earlier contacts) but there are still things that could have been done, and which you can only really think through if you’ve had some prior training or experience. I’d recommand that the gym finds a good conflict resolution training course – as opposed to self defence, which is a different issue – (a one day course should be absolutely fine) and send ALL their public facing staff on it. It will pay dividends.