You should initiate disciplinary proceedings against the workman following the Standing Orders of your establishment and the provisions of Industrial Disputes Act. You have to comply with each and every point of law and principles of natural justice before an employee is terminated or dismissed on the ground of misconduct. It is advisable to issue a show cause notice to start with and get a reply for that. If the reply is found unsatisfactory then proceed with a domestic enquiry and issue the charge sheet. Then conduct enquiry by appointing an enquiry officer from outside. Serve notices of hearing in time and record appearances of himself and witnesses. If the enquiry officer finds him guilty, then give him anther notice stating that you will rely on the findings of the EO and then discharge or dismiss him.
For a brief idea of the steps involved please visit my blog to find a ppt on Disciplinary action. Madhu.T.K: Disciplinary Action