K.P.
Yup. I was doing a workshop for 60 teachers who were being insanely rude (this had actually been going on for 6 months). I had been up all night with a sick toddler, hadn't eaten all day and it was hot in the room. A group of the teachers decided that the presentation wasn't relevant to them and decided to use the time as a coffee hour, complete with snacks, texting and chatting. I tried all of my "tricks"... moving closer to them, stopping the presentation and staring at them, clearing my throat and asking for their attention. None of it worked, so I said LOUDLY into my wireless mic "Your students are failing and your school may be closed... could you PLEASE try and pay attention!"
So much for professionalism. I did take the opportunity during our next meeting to review our expectations for one another and to revisit the purpose behind our work. I apologized for losing my temper, but didn't make excuses or a big deal about it. Things happen & we're human. Apologize for speaking before thinking and go on with business as usual!