(hint: the shy kid probably did not suddenly decide right this moment to pop up and decide to fight for alpha status)
The teacher(s) new exactly what had happened. The administration didn't, though, and it was them that threatened to suspend me.
They did account for the circumstances; they brought in the bullies parents and all of us sat around a table to discuss it. But he squirmed out of it ("so sorry! Only a bit of fun", etc.).
The problem is; it's only when the bullied person does something extreme that the bully gets into that situation. And it didn't happen often, so this particular individual had lots of "last warnings" and final promises to be nicer.
But no one followed up and punished him properly the next time.
Teachers are there to educate, they aren't equipped properly to deal with a point of justice/behaviour.
That looks like it is a significant part of the problem: the adults most likely to exercise good judgement on these matters (teachers) don't have the power to do so.
We have to triage the problem. First, prevent harm from occurring to others. Second, attempt rehabilitation.
Remember that bullies also create problems in other kids which can force them to act out. Force them to drop out and get into drug use. Force them to become bullies themselves, or thieves, etc.
At a school, the adults are the system, so I think my point still stands.
I've long wondered what would have fixed this... in the end the only solution I could come up with would be to segregate the consummate bullies. I'm sure smarter people could think of more adroit solutions.
With the above, a reasonable adult, considering evidence, has no choice but to "arrest" the kid with the chair, since the other has done no wrong other than verbal + possible pushing.
The system needs fixing by making what the bully did prior to the event actionable by the adults so it wouldn't escalate to where it did. Cameras would help.
But then what do we do with the bully? Move him to another school and let the cycle repeat?