@FBM,
Cops in the UK don't carry firearms, and that's the reason they don't kill civilians for good or bad. When cops in the US carry firearms, they tend to use it when it's really not needed in too many cases.
It's probably sensible to have more cops in communities where crime is common such as Oakland, Detroit, St Louis, Birmingham, Atlanta, Baltimore, and Cleveland. It's about cost vs benefit. Our town, Sunnyvale, California, has the right combination; our officers are both police and firemen.