Resignation while on probation - employee threatening to call the police on us

I am HR Manager at one PVT LTD. One of our employee joined company on 1st of month and on 3rd day he had some verbal fight another employee.. and he told me he don''t like to work here. I try to confirm that he is on probation don't do that. He did not agree with me and on 16th of the month, he gives me a resignation letter dated the 11th of the month, by writing that he is leaving on the 27th of the month. On his first day, I already confirmed that 30 days resignation letter is a must.. now he is threatening to call the police on us...

His threat of police is empty.
But does organisation require such immature employees.
Let him go.
Settle his amounts due etc and peacefully allow him to exit after checking that he does not hold company property etc..
His relieving papers can clearly mention reason for exit.

During ongoing Probationary Period, No Notice to Quit Emploment is required. The Probationer vcan be released / Discharged with imm effect after s/he returned Company's/Est's Property issued to him/her to carry out his/her Duties
Kritarth Team,
26 Nov 2018