Alison,
If you call 911 inform the operator that your difficult child has a mental illness & needs safe transport. Before I learned to do this, it was labeled as a "tantrum" & when I hit the hospital with a violent wm, things were not taken seriously.
On the other hand, now I call 911 & the police come into my home before they will let EMTs in - domestic disturbance. Sometimes, you just can't win.
I don't care anymore - it gets the help that is needed.
Keeping you in my thoughts.