Unfair treatment in a work place

I don't even know where to start, our five star hotel is becoming toxic... since December month 2019, new management stepped in, company policy and values are not adhered. We have been having a problem with the executive chef, he is treating employees unfairly. Apparently the company is not paying overtime but some employees work long hours, it is very unfair and wrong...Some employees are resigning , it is so said to experience such. This chef is killing every employees passion. He screams, swear and provoke other employees when he is under pressure, it is so wrong, we all have feelings as we human beings. We have currently launched a grievance against him, the new general manager is a friend of him, we not sure if she will understand our matter. We really need your help. Employees were called today, 2 employee at a time to the office, by the general manager... I find it wrong for the general manager to just question without having the 3rd person to take notes and be fair on this serious matter.

Please help