I haven't seen anything like that go down in group but I witnessed it inpatient several times. I would head straight to my room until it was dealt with and depending on how hostile they were I might take a PRN. I think the reason it's so horrible is that you don't know the people well enough to know what they're capable of.

I'm sure you're shaken up but you took care of yourself by leaving and hopefully those two will be banned from any more meetings.