There is no evidence that he made any action to give the remotest, faintest, slightest hint in any way that he was going to suddenly decide he was going to win in a shoot out against 23 armed officers .. him with his trusty single gun, them all with semi-automatic machine guns.
Out of interest, what about if the police thinks some one 'may have a gun, but may not' .. are they also allowed to execute them in the street then?
If the suspect is not co-operating and is suspected to have a gun, yes they can eliminate the thread, stop using the word "executed" you know its a wrong word to use.