First, there is no such thing as a bullet proof vest. There are bullet resistant vests, but they don't stop ALL types of bullets and those difficult criminals haven't yet let cops know in advance what kind of guns and ammo they plan on using on any given day.Cops should not carry guns. They should wear bullet proof vests and helmets, and should travel in groups, so if someone starts shooting at them, they will be able to subdue that person without guns. When society starts trusting cops with guns, that's the start of the road to a totalitarian dictatorship. We've been on that road for hundreds of years now, and we keep getting closer to that dictatorship. Is it too late to take a detour and find another route?
Second, just suggesting that an unarmed group of people should try to subdue an armed assailant shows just how stupid you are.
Finally, its not when society gives guns to cops that oppression starts, it's when the government disarms it's citizens. So, as suggested, try England out because that's where they do exactly as you preach. Cheers