Why suspended from work?

My friend had been given a hard time at work for wearing a turban, he's Sikh. So, Human Resources suspended him and they're doing an investigation, hes getting paid while hes suspended until further notice, why would they suspend him? Theyre doing an investigation to see if he really was harred... How do these cases usually wind up? he works at autozone, and the dress code states only black hats / autozone hats allowed.