Excellent 6 year Employee completes shift and meets relief at door outside of post. Goes to restroom and returns to be summoned for training by supervisor. Completes training and returns to post for 30 minutes until post is properly staffed. Later fired f

The employee has worked 6 years perfect attendance, good reputation, on every response team, military veteran, etc with no disciplinary. No bathroom in unit, 12 hours without a break. Left post at shift change met relief at door. Did number 2 returned to get things in 20 mins and was called to supervisor desk for training. Completed training and told to clock out. Officer departed properly staffed post. Later determined the relief officer did not enter the unit for 53 minutes. Departing staff member fired for post abandonment. Is this legal?