Hey bro,
I tend to agree with ode to a grasshopper here, the TF's missing are a side issue to cutting hoses up and being suspended from school.
There could be a problem that the young bloke is dealing with that he can't talk about/explain (bully at school, problem with a teacher etc). There is support out there that may help you all get to the root of the problem. QLD health will offer some advice on who to see, you could also see a councilor at school or freecall Lifeline or parentline, they provide free professional advice and support and know how to get info out of kids and offer advice.
These are just friendly suggestions and thoughts.
Good luck mate, hang tough.
Talk to you later in the week.