Anti-police? Gang related?
Gangsta rap evolved from hardcore rap, and that genre originated in the early 1980s. The difference is mainly in lyrical focus- not all hardcore rap songs are gangsta related, but many are. Run-DMC popularized the genre style, then Too $hort and especially Schooly D were early exemplars of acts that started bringing up that kind of stuff 1983-86.
NWA’s classic anti-police brutality song, “F*** the police” dates to 1988, and it wasn’t the first of its kind, just the most famous. KRS One’s “Sound of da police” came in 1993, and is about driving while black.