Nothing has to happen for someone to out as trans, we simply are just born this way and we feel we are in the wrong body. This can be both distressing and also uncomfortable for us, we need some type of support, I am trans F to M my self and honestly nothing happened, I have felt as if I was born in the wrong body and the wrong gender all my life, I just did not understand it until later on in life. My advise to you:
-Call them he/him NEVER use her/she, this only make us remember the one thing that makes us so miserable.
-Be supportive and when they get their period do NOT tell the something on the terms of "suck it up" this is a female specific problem and for most/some one of the things they are discussed by that their body does. Understand that to them their mind and soul are male so this sets off an alarm to them and they could freak out panicking, because we think like a male, if a boy's penis started bleeding they would or should be highly concerned and freak out.
-Don't ever give up on them. It can be frustrating wanting to help them but not knowing how or being able to.
You need to accept this, remember you did nothing to make them this way and nothing had happened to make them this way. This is just how we are born, do what ever you can as soon as you can to get them what they need, it is like living in hell being trans because our body is more a prison, thanks to being born the wrong gender. Good luck to you!
