Mr McCormick and the property owners gave first aid before Mr McCormick finished the installation. This took a couple of hours and then Mr Narayan was taken to the doctor.
The property owners differed about how serious it was.
The man, a builder, was said to have told Mr Narayan to "harden up" because the half-inch cut to his head was only a flesh wound, while the woman was more concerned.
Mr Narayan told Mr McCormick not to report the incident if it would get him in trouble but Mr McCormick did so.
A couple of weeks later he was fired for "gross misconduct", but authority member Robin Arthur found the Compass Communications' processes were unfair.
The authority found Mr McCormick wasn't given all the documents associated with the incident before a meeting with his employers, the possibility of dismissal wasn't discussed with him and he was not told a report from the firm's human resources department had recommended his dismissal.
This deprived Mr McCormick of the chance to talk to the company about this.
"Accordingly I concluded [Compass Communications] had not acted as a fair and reasonable employer could have in all circumstances at the time, with the result that Mr McCormick's dismissal was unjustified," Mr Arthur said.
"Mr McCormick's actions could have been found to be serious misconduct. What was not justified was the fairness of the process, including the decision to dismiss him."