The video is interesting but there are parts I find a bit weird.
As the taxi stopped, why did Duggan immediately open the door and jump out? It doesn't feel like a natural thing to do to me. He was obviously aware of what was occurring before the vehicles finally came to a stop, you would think that he would just sit and let them approach.
Why was Duggen apparently jumping out of the taxi with his hands inside his jacket and one hand - seemingly - in his pocket? This doesn't seem natural at all.
The most likely scenario (IMO) was not put forward on the video; The taxi door was most likely opened well before the vehicles came to a stop. Duggen knew what was occurring and knew he had to get rid of the gun. I reckon he opened the door and threw the gun over the fence several metres before it came to a stop. That would explain why it was at an angle several metres back, and not in line, and also why nobody apparently saw him do it. They were all distracted by the boxing-in maneuver at the time.
The idea of him throwing the gun during the course of being shot is utter nonsense. Why would he do that? Everybody in close proximity would have seen him do it and he would be well aware of that.
Equally, why would an officer take the gun from the taxi and plant it over the fence? The only way that benefits the police version is if they said they saw him throw it - but nobody did.
Personally, I have always thought that police who are attracted to the gun squad are probably the people you would least want in charge of guns.