Anyone familiar with the law? Husband fired w/o notice

So my husbands boss came to our house today to give him a termination letter & his last paycheck. The letter stated he has not been working full time hours and he “bad mouths” the company. There has never been a write up/discussion about the behaviors. Don’t they need these things documented? We also have text messages of his boss telling him there’s “no work and he shouldn’t come in”. There’s no handbook for this company stating rules. He’s been there over 10 years with no benefits or anything. Is it worth getting a lawyer? We live in Illinois.