They are downsizing, getting rid of most full time positions, and replacing them with part-time jobs employing more people for less money by giving fewer hours per person. Companies save big this way because they are not required to pay benefits. But it will be hard to defend the involuntary termination of fulltime employees in a short amount of time. This looks like they were laying you off in a downsizing and possibly trying to avoid unemployment insurance payouts by firing the employees rather than laying them off.
I'm sure neither of those unethical company ploys will make you smile but at least it may clear the mist so you can clearly see and understand what may have just happened. Sorry that you got caught in the ugliness of the company's situation.
Google this company and see if you can find a corporate backdoor to their superiors and HR and have all this looked into. The fact is they have placed your reputation on the chopping block in addition to firing you. I'm praying for you and asking God to guide you and protect you through this very messy unnecessary situation. I hope you will attend state provided job search workshops, training and support. The employment specialist can help you navigate the minefield this employer dropped in front of you and exercise damage control. It will be necessary to address the fact you were terminated. It may be necessary to minimize the damage of the charge with careful wording. To say you do not fully understand why your we're let go right after 3 other full-time employees were let go may suffice. Or you may be able to go with a serious misunderstanding led to your involuntary termination. Talk to an employment specialist.