The problem is that once the perps turn and leave that ends that situation !! They're no longer a threat . If you then attack them you have just initiated a second situation !!You are now the attacker not defender !
I remember such a case .A woman is raped but offers no resistance perhaps because of the shock. The perp then leaves and she follows , picks up a brick and beaks his head severely. She is found guilty of assault !
The cases discussed in this part of the forum show again and again that you sould get the best training you can find !
And Watson , bring your revolver !