All on-duty officers are supposed to wear a vest, but even then it's only protective against specific bullets and who the hell knows what type of weapon and ammo someone has now a days. And you can still get shot in the leg or other major artery and bleed out...then there's the head shot.
Thought of this the other day and it's like you need to invest in technology that scans and looks for a gun. I have no idea if that's even possible, but some type of X-ray vision. It sounds kind of like a movie or Terminator type solution, but damn, any idea or solution is way better than just police officer training and some additional laws that attempt to make owning a gun more difficult.
Even having annual psyc-tests for anyone who is a registered gun owner. But you know damn well there are loads of people who have guns and those weapons aren't registered and those people with unregistered weapons aren't supposed to have a gun.