If any member is injured or contracts a disease during his first 5 years of service in his department which, in the judgment of the Board of Police and Fire Surgeons, disables him from performing further duty in his department, and if the Police and Firefighters Retirement and Relief Board finds that such injury or disease was not incurred in the performance of duty in his department, such member shall, upon the approval of such finding by the head of his department, and without regard for the provisions of any other law or regulation, be separated from the service.