The massacre of law enforcement officers in Dallas was the latest gun tragedy in the extraordinary life of the city's police chief David Brown.

Mr Brown, 55, lost both his brother, and first police partner, to gun violence.

Most painfully of all, six years ago, his own son shot dead a policeman and was then killed himself by other officers.

Mr Brown, who is black, grew up in a rough neighbourhood in South Dallas and describes himself as an "inner city kid".

Having seen firsthand the ravages of the crack cocaine epidemic in the early 1980s he became passionate about joining the police force.