I think all positions of power attract some knobheads, to be honest. Politicians, teachers, police officers.
I don't really think it's fair to pick out isolated incidents though and paint a picture like all police officers are untrustworthy.
As for Duggan, it's rational to wait for evidence before saying what was right and what was wrong. If he did have a gun though, and had it in his hand, then I don't blame the police for shooting. What's the alternative? Waiting for him to shoot?
So what if he was a father of four. It's tragic for children to lose a parent, but if the parent was waving a lethal weapon around I think it's their own irresponsibility that's left their children fatherless.
That said it's fairly hard to garner reliable evidence, considering the main source of information in this country is the media, which is less reliable than a chocolate teapot.