A senior editor for PC World Magazine was fatally shot in his home in what authorities said Wednesday was a drug-related attack. Rex Farrance, 59, the San Francisco, California-based magazine’s senior technical editor, was shot in the chest after four masked men broke into his home Tuesday evening, Pittsburg police said. The assailants also pistol-whipped Farrance’s wife, Lenore Vantosh-Farrance, 56, a registered nurse. She called 911, but the attackers fled before officers arrived. No one has been arrested, officials said.