Termination after resignation sent through mail

I son was working in a software company having less than 20 employees and was provided with appointment letter covering terms and conditions and including bond of two years , Ther was emergent situation where He had to take care of grandma of her old age , applied leave and after few days , there was mail from employer theatening to take legal actions giving many reasons of indisicple which was non existant , through email and My son responded to his mail point to point and the was mail was sent and emergent situation , My son resigned on email , for which employer replied to take care of grandma having gone through the mail , after one month employer has terminated the services and threated to take legal action including police complaint 1. Can the employer can take action on me 2. what actions my son need to take immediately