Sorry, Bud, I was on an iPhone, so thread searching was even more of a pain at my end...
Anyway, if the agent was still engaged with the BG when the off-duty and retired LEOs arrived, that would pose certain challenges for the responders. From the perspective of a potential responder, you have to determine who is who and what is what before pulling a trigger.
From the perspective of somebody in the agent's position... one has to be ready for the arrival of LEOs. There have been other threads where we've discussed that one trait a carry holster should have is sufficient rigidity that a gun can be holstered one-handed, by feel, in case one needs to watch the BG but doesn't want a gun in hand when LEOs arrive. Some people wondered why I thought that was important. This case may have provided an example, had it gone differently. (Since it is not clear if the agent had a drawn weapon, or may have been actively scuffling with the robber, when the LEOs arrived.)