File a union grievance as soon as possible. The clock starts ticking on minute one of being let go. Each contract is different but you have 7-8 days for them to do this. If you're in a non union position well it's just like any other job you're screwed. Well on the plus side you should be able to apply for unemployment. But good luck with that. 

Job abandonment? Going too slow at your work? Goofing off instead of working? Not showing up for your shifts? Handing off your shifts to another coworker? Bad attendance? Being late all the time? Making up your own shifts? Doing another job instead of the assigned one? Putting your phone before work? Putting your hobbies before work?