I am speaking from personal past experiences that I wish I could go back and change. I let my then union boss talk me out of pressing legal charges against my superintendent assaulting me and I was removed from the job the next day. ME, the victim of assault from my boss, removed from the job instead of him. That boss stayed at that job for quite some time afterwards. I know now that the proper response to a work place assault is to call 911. Don't discuss it with your fellow workers. Don't call your union. Don't ask for your steward. Don't debate it with management. It doesn't matter if the assault came from a helper, foreman, superintendent, or company owner….
CALL 911 FIRST
You can take care of all that other stuff later. You can talk to your union boss and steward later and bring the assaulter up on charges later. Call 911 first and have the violent criminal removed in handcuffs. You do not know if their rage will escalate. You do not know if they have a gun, or a knife, or are planning to go out and get a weapon.
CALL 911 FIRST