The Kidnapping of a Street Gang

The movie is set in kind of scuzy new york from the seventies. The kidnapper goes, i want you to leave a million dollars for me in this parks department structure. It's right next to where a big outdoor rock concert is being set up. And boyd starts chasing him through the rubble of the south bronx. But then that street gang shows up. They're roughly 500 members of the street gang and they all try to kill boyd. He's just fighting them off like crazy, until police show up and start arresting everybody.