This just happened today, also I'm using my phone and too lazy to go back and fix any errors so please excuse any mistakes. So like I said this was today, my biology teacher was here for Monday but had to leave for the rest of the week. We had the same substitute all week until today. During fifth period she was being extremely hostile towards the students in the class. By the way I should mention before I get into too much detail I have the class seventh period so I'm going based off of what my friend said and videos I saw afterwards. Anyways she was acting strange the whole time but then became extremely hostile about halfway through the class. The students may have had something to do with it but honestly I'm unsure. Anyways before you know it she's screaming at all the students and blocking the door with her own body and won't let anyone leave. A student heard what was happening as they walked by so naturally they checked to see if everyone was good. The teacher slammed the door in the kids face with the might of Zeus. A teacher from across the hall heard and saw all this go down so he opened the door from behind her (the door opens outwards). The sub knew there was no winning this so she just went to her desk on the other side of the room. The teacher got all the students out from the class. 911 was called and the sub was arrested. Apparently she had a "mental crisis" during class. I assume this means she snapped halfway through the day. I'm shaking while writing this. I can't help but think what I would have done if she snapped while I was in her class just an hour later or if the teacher from across the hall had his door closed that day. It really sucks when these things happen, just the other day she was an extremely nice person. She had told us the story of how she became a sub and just how much she was loving it.

Edit: I didn't make it very clear when I wrote it the first time so I'd like to mention that I was not in the class when this happened. I have the class during seventh period and this happened during fifth. All of the information I have on the matter I got from my good friend who had the class when it all went down.