Really sad news, It's a sad day for comic fans. Al Feldstein was one of the All Time Greats. E.C. Horror and Sci-Fi comics are some of the greatest comics ever made, and Al Feldstein had a huge part in the operation. Then he took it into overdrive with Mad Magazine, the magazine that changed the face of satire in the USA.
His work had such an influence and appealed to so many people. I, for one, know my childhood would have been lacking without Mad Magazine's subtly subversive presence, and my teenage (and college) years would have been severely lacking without my hefty hardcover E.C. reprints. My condolences go out to his family.