I think the answer is he suspected, and attempted to investigate...
He was aware of the robbery call.
He saw someone who might be involved.
And in the course of trying to investigate somehow the SHTF.
The Chief needs to make up his mind with the facts.
The guy was either stopped because he was in the middle of the street or because he had cigars in his hand.
It’s one or the other.
If it was cigars and he thought he had the suspect then protocol is to call that in.
Did he call that in???
I’m confident that the officer knew Brown and his friend were suspects.
The call referenced a robbery which is a crime against a person, not a crime against property. Most departments encourage their dispatchers to gather as much suspect info as possible. Most times the radio operators broadcast this while units are enroute to the scene. Typically one unit goes to the scene while other units go into the area to search for suspects. We don’t know if an officer had arrived at the scene yet. If he had, he would have confirmed the crime and suspect info first.
In my opinion, when Brown decided to go after the officer’s gun in a one man unit, unfortunately, he wrote his death warrant. This is a scenario which every officer has thought about before it happens. You think about it on the first day you hit the streets. And, every officer has made up his own mind about how he would react.