In July 1985 photographer Ken Regan had just started shooting Madonna
, the Rolling Stones, Tina Turner and other A-listers backstage at the Live Aid concert for PEOPLE when the lights went out. "He was cool and calm. He had a backup camera and batteries," recalls M.C. Marden, the magazine's photo editor at the time. "That's a lot of star power in one little group shot, and Ken made it happen." Before he died of cancer Nov. 25 at 73, Regan also captured intimate glimpses into the lives of luminaries as varied as JFK Jr., Muhammad Ali and Mafia don Joe Colombo Sr. "You can't treat all celebs alike. You have to understand how to flatter them, how to push them," says People's founding editor Richard B. Stolley. "This is what Ken was genius at." And that will remain his legacy. "He was well-read, a sports freak and a news junkie," says his close friend, photographer Neal Preston, "but he would want to be remembered as a consummate professional who always came back with the goods."