COLLIER TOWNSHIP, Pa.—A former neighbor of a U.S. Postal Service worker in Pennsylvania confessed to authorities that he fatally shot him because he believed the mail carrier previously poisoned him and his family with cyanide, a federal official said. Eric Kortz, 53, turned himself in Thursday for the shooting death of Louis Vignone while Vignone was on his route in Collier Township, acting U.S. Attorney for the Western District of Pennsylvania Stephen Kaufman said in a statement. Vignone was shot around 10 a.m. Thursday while he was delivering mail, news outlets reported. Federal authorities said Kortz told investigators that he drove up and stopped in front of the USPS vehicle, then opened fire. He then dropped the gun and went to a borough police department to report what he did, according to an affidavit. Kortz also told investigators that he and Vignone used to be neighbors. Kortz said he believed …