Death Threat and Assault from CIT employees

I've just been assaulted in public by employees with Fidelity ADT uniform, driving Fidelity ADT vehicle, presumably having received training from ADT Fidelity. Vehicle serial number 44680, number plate: JG 95 JX GP. Location Maake plaza, Tzaneen, Limpopo. I couldn't get their names but one of them threatened to shoot and kill me for walking past their truck. As I tried to explain that I had nothing on me which could be seen as threatening and needed to get back to a shop to complete my shopping, I was verbally insulted and threatened. I walked passed and continued on my way, unaware that an ADT Fidelity employee was following me. When he caught up to me, he then proceeded to slap me violently, unarmed and posing no threat (having walked away from the incident). Having recently had treatment on my leg for dislocating a knee (walking is a pain that I don't enjoy prolonging); please advise on how I should have handled the situation better as not to be violently assaulted and have my life threatened.