Harassment thru whatsapp by CEO of school

I am a secondary school teacher just 3months old in SSC school . The CEO uses threatening whatsapp replies towards me when i approach him with technical questions. i dont have a choice as he himself handles all technical queries of the teachers. recently he said he will put me to shame when i asked him what was my fault. Thus i quit immediately feeling threatened by him. Now he has asked me to pay 3months notice money and then he will release my Original certificates. I have hardly worked 3months, how to give him the money back. I would have worked but i feel scared to go to work now. To work, you need some peaceful working conditions. I have also told him within a month of joining that i wanted to quit. The principal did not allow me to do so. Now after 3months the situation is still the same- threatening. I have filed FIR at the area police station thru post yesterday. I have not heard from the police about my complaint yet. Maybe the police have not received my post yet. Please advise how to get my Originals back without having to pay.