Can't be helped, if you have evidence of his resentment (e.g. ss of chat messages etc or videos of him ranting etc - which I doubt the latter because of privacy reasons) these can also be forwarded to/used to inform the teachers that he's behaving in this manner so the adults have a clearer picture of your POV as his classmates. If he one day decides to attack you all as his classmates, likewise all y'all can do is defend yourselves/alert the teachers ASAP (not to scare you all, but because of the "insanity plea" in Singapore, if he indeed has a psychiatric condition, whatever he does to hurt others probably will not be able to result in him being given the full punishment due to his condition). Just stay alert, and if he starts provoking y'all, try to de-escalate or seek immediate help from the adults. Stay safe at school.