Deconstructing a few paragraphs from this source here s what happened according to Assistant Commissioner Simon Byrne 14 20 first 999 call about a man being attacked but with no mention of a gun 14 24 first 999 call that mentions a gun armed response unit assigned 14 29 first unarmed officers arrive at the scene establishing a cordon and waiting behind it for the armed response 14 34 first armed response officers arrive If correct this seems normal to me Armed police are not common even in London And if as it appears the first unarmed officers on scene had already been told they might have a gun then staying behind a cordon until the armed officers arrived and them then shooting them as they advanced would all seem standard procedure