First there are 3,000 lawyers in the phone book/internet in the area you live. Start there and ask for a reference to a labor lawyer.
Second - Update/Create a resume
Third - get in touch with your states unempleymet office. That can help suppliment but will not completely replace your fathers income. Some states let you do all the filing online.
Third - Start looking at some other skills that your father can exploit. Maybe a transition to a sales positon. Most are very low, if any, physical effort and after 14 years of laboring he must have use some type of raw material, tools, or products that he has gained knowledge of. Exploit that product knowledge in the field of selling or even customer service. If your pops is not the outgoing type, there is always inside sales where he can rely on that accumulated knowledge to help customers with the "know how" they need.......
I will tell you that if you are in a state like FL or CalI. an employer does not need to have a reason to fire you. Most full time employement that is not under contract is considered "at will" by both the company and employee and that company or employee can terminate the employment at any time, WITH OR WITHOUT CAUSE. They could have literally told him that they did not like the car he drives or told him nothing at all. I think the legal battle will be uphill all the way. A company usually has a legal department and usaully far greatter resources than an individual will have. They can fight the harder fight which usually means they will drag things out for years and try to out last you guys.
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Does it sound,based on what info you have supplied, that your father was treated unfairly? Sure does. Does a company have any legal obligation to treat it's employees well or even ethically? Sure don't. Remember that companies have two goals....Make money and protect their ability to make money by all available means.... I know I have not provided exactly what you are looking for but I had to deal with similar situations from both sides of the fence and I hope this will help provide a little guidance for you during this rough time.
Good luck to you and your family........