Harvey Marcelin was the center of gossip Saturday in Tompkins Square Park, where acquaintances marveled at the accused killer’s alleged ability to dismember a human being while in a wheelchair. “She chopped someone’s f—ing head off. She actually severed someone’s head,” blurted Junior, a homeless man in the park frequented by the serial killer. Marcelin, 83, is a transgender woman and two-time convicted killer charged this month with the gruesome dismemberment murder of Susan Leyden, 68, of Brooklyn, who will be laid to rest Sunday in Paramus, NJ. Leyden's body parts were found in several Brooklyn locations. “She was in...