When I lived in the Bronx, in the early ’70s the subways (not underground in the Bronx, they ran on elevated tracks over major streets but were still called ‘subways’), were havens for criminals and drug addicts. In NYC the these were patrolled by transit police. When they’d go into a subway station at night, they went in teams of at least 2 officers. One had a doberman or a shepard on a long leash so the dog went around corners first in case there was a mugger waiting for a victim. The other cop carried a 12 gauge shotgun – this was before cops were armed with M-16s. My dad had friends who were transit cops, they used to complain that the 12 gauge shotgun blast really had a loud echo when discharged in the subway stations. But they said it stopped the biggest mother f**kers in the Bronx. I don’t miss my home town one bit!

https://abcnews.go.com/US/homeless-advocates-slam-nypd-deployment-600-officers-patrol/story?id=75945015