Under what circumstances can you say 150 armed police, some to most having good protection and all with decent weapons, are justified in not engaging a shooter over apparently something that went on up to 90 minutes? If the city mayor or police chief said no police can engage the shooter because they want a high civilian death rate, would that make you happy? There is no other plausible reason for people, meant to engage, to not engage.
These same people gladly pull a speeder off to the side of the road, but that earns the city cash income from a ticket, and it doesn’t help depopulate an overcrowded Earth.
My answer to this, is I don’t know enough facts. I don’t know the details of their training or orders in how to approach a situation such as this.
“If the city mayor or police chief said no police can engage the shooter because they want a high civilian death rate, would that make you happy?”
I would be shocked if anyone in authority gave such orders. I would not be happy about that.