Green’s Dictionary of Slang

agent n.

[an agent properly works only for the FBI and is not, as such, a police officer]

(US black) any police officer.

[US]B. Jackson Get Your Ass in the Water (1974) 206: The room was filled with reefer smoke, / one agent got high and soon told a joke.
[US] ‘Sl. of Watts’ in Current Sl. III:2.