Seems hard to say given the lack of experimental data, but an interesting question.

I once read that there’s a common mammalian threat-response neural network that generates flight behavior if the threat is far, freezing at medium distance, and fight up close. How the distances are set varies by species.

Based on that, fighting could be the expected reaction in this situation, but I think humans are a little different. A nearby human threat can generate other responses such as submission, begging, or tending. He had to realize those wouldn’t work and suppress them. Someone could appear to freeze if they were trying to decide whether to fight but having a hard time making the decision under stress. It probably helped that the killer appeared somewhat confused, therefore was not exerting any emotional dominance and was more vulnerable to counterattack.