Afaik he was armed and on his way to essex to kill the bloke who killed his cousin. He was a well known class A dealer and was (unfortunately) looked up to by the local kids as some kind of elder and hero.
He was scum imo and got what he deserved.The police were most likely acting on a tip off and stopped the cab he was travelling in. No doubt mayhem and confusion ensued and a cop let off a round which in the confusion was thought by another cop to have come from the armed gangsta - so he shot him.
Who cares ? 
I dunno Albs .
After reading the article it looks like only two shots were fired , both hitting Duggan , one of which ricoched and lodged in the other Officers radio. That leads me to think that he either went for or drew the weapon thus giving the armed officer the ( legal ) right to fire.
I'm in no doubt though that those Pariahs known as human rights lawyers and campaigners will call it an execution of a thoroughly innocent victim and along with the pond life that held him in high esteem once again vilify the Police for doing their job.