Until they have clearly disengage they are still a threat.Didn't watch the vid.
But if a person is ever placed in a position where they have to discharge their personal protection device, and the perp turns around and starts to run away, I think any reasonable person would understand that the perp would later attempt the same, or worse, crime against another. Thus continuing to fire should not result in punishment. It is merely protecting some future person from being the victim of a crime.
My idea of "threat" and someone else's idea of "threat" are totally different.Now, if you chase them around a corner or something, you'd better have a spectacular explanation for why they were still a threat, but just turning away or diving for cover is not enough IMHO.