Legal Question in Disability Law in Massachusetts

there has to be demonstrated that that was the basis for firing the person and if so the case gets filed with the MCAD

You cannot fire an employee who is disabled if the reason you are firing is due to the disability (so long as the person can do the essential functions of the job with or without reasonable accomodation). However, a disabled employee is not exempt from being fired. However, given that the employee is disabled, you should proceed carefully and should consult with counsel.