Well Dang it, the officer really lost the plot when the fella pulled the gun didn't he. That was pretty bad.
I'm not any kind of expert on tactical matters, so I don't know if that kind of pants shitting can be trained or drilled away. But I don't think firing an officer that got shot and nearly killed in the line of duty when they did not shoot or kill anyone else is a good idea in general. That's the kind of thing the people we really want to be cops take a long hard look at when deciding to become, or continue being, a cop.
Being a police officer can be difficult and dangerous.
The PO de-escalation efforts were not great. But he was not making things measurably worse and the fella was definitely not right in the head. He went from stating that he wasn't going to leave to demanding to leave in about 10 seconds. But shit did not really hit the fan until they made physical contact with each other. From that point on it was pretty much a trainwreck.
I think that would be my big takeaway from this. That moment of contact was pretty much the Rubicon. The PO should have either started grappling with the guy immediately to keep him in the room, or he chould have just let him out, followed at a reasonable distance, and continued deescalating efforts. Probably either of those would have been OK.