L.A. Wars — Carl Ramm

Hawker throws himself into a cutthroat gang war in Los Angeles

In a pawnshop alleyway, James Hawker finds a body mutilated beyond recognition. She was beautiful once, he knows, but life in this hardened Los Angeles neighborhood took its toll. Starnsdale was once a working class community, but now it is a battlefield ravaged by warring gangs who kill without thinking and care nothing for the ordinary citizens crushed beneath their feet. The toughest gang is called the Panthers -- and Hawker has come to hunt them down.
 
Enlisted by an Illinois millionaire to stamp out organized crime across the country, Hawker attacks the Panthers and their rivals, the Santanas, at the same time. As the two gangs consume each other, and Starnsdale's gutters overflow with blood, Hawker sees a chance to end the conflict once and for all, and bring peace to a troubled city.
 
L.A. Wars is the 2nd book in the Hawker series, but you may enjoy reading the series in any order.