I made friends with my high school biology teacher due to our mutual interests in horses. I used to go out to her house after school and help train some of her animals. Anyway, this teacher was notorious for being a little unstable and her going into screaming fits wasn't unusual.

I don't recall the circumstances, but one day a student pushed her too far and she completely snapped. She was literally screaming (no words, just belting it out) while pulling her hair. After a moment, she came to and slammed the classroom door shut, proceeded to tell the entire class they were terrible human beings and were the reason she was going to end up in an asylum or doing drugs. She then rushes out of the room and disappears down the hall. We're all sitting there stunned. Nobody makes a peep. She's gone for a good 20 minutes before sheepishly coming back into the classroom, saying she has an upset stomach and needs a break, puts on a movie and leaves for another few minutes. When she came back, she pushed all the belongings off a student's lab table, climbed on it, laid down and took a nap for the remainder of class.

We had plans for me to go to her farm that afternoon and, needles to say, that was the most awkward car ride of my life. She acted as though nothing happened earlier that day.

TL;DR: teacher got so angry she had to throw up, took a nap on a desk and continued our plans to go horseback riding.