What went wrong is hard to guess. It could be that the dog had been trained to fight or at least defend the owner. The dog could have become scared and reacted badly. Although such breeds of dog have a bad reputation many turn out to be good house dogs and not all are attackers. When such a dog attacks though it does not take prisoners. The officers must have been terrified.
The police at the scene were obviously overwhelmed and had to call in reinforcements. Members of the UK armed police attended and the dog was shot dead.
The incident took place at around 9am in Albert Square Stratford. The injured Metropolitan police officers were all from Newham. A 20-year-old man in now under arrest.