Husband let go

my husband was which he is a protected veteran was terrminated from his job they say because he had a bad attitude but knew he has ptsd when they took over where he worked at for over 2 years they knew he didn't let his ptsd stop him from being the best worker they had but let him go and everyone that worked their for the company they was contracted in at has even said how he is the best person the contracted company had..I know that we are a at will state