A former East Hampton High School football star who, police said, used his Sag Harbor neighbors’ mailboxes to deal heroin in that village, was charged on Friday afternoon with two felonies, possessing heroin with an intent to sell and actually selling it. Joseph R. Dowling, 24, was arrested after East Hampton Town police detectives coordinated a buy-and-bust operation on Lighthouse Lane in Sag Harbor.“We developed some information and we were able to run with it,” Det. Sgt. Greg Schaefer said Tuesday. An undercover officer reportedly made a buy from Mr. Dowling, who, the sergeant said, was using the Lighthouse Lane mailboxes first to drop off the narcotic, then to pick up payment. Mr. Dowling, who lives on nearby Brandywine Street, was also charged with possession of a hypodermic needle, a misdemeanor.At his arraignment in Sag Harbor Village Justice Court Saturday morning, Justice Lisa R. Rana entered a denial to the felony charges and a not-guilty plea to the misdemeanor. The defendant’s mother was in the courtroom, tears in her eyes. When Justice Rana set bail at $11,000, she softly said, “Oh, my God.”In addition to the current charges, Mr. Dowling will likely be charged with violating his probation in connection with October 2014 charges, opening the door to a possible re-sentencing in that case, which also involved possession with intent to sell and felony possession of heroin. The earlier arrest followed a chase at speeds of over 100 miles per hour on Route 114.Afterward, he was allowed to enter a drug treatment program. On Feb. 4 of this year, all charges except for two misdemeanors were dropped, and he was sentenced to three years’ probation.As a Pierson High School student, Mr. Dowling played both sides of the line for the 2009 East Hampton-Pierson-Bridgehampton Bonackers, who made the playoffs for the first time since 2003. He was named all-county in his junior and senior years.The district attorney’s office is reportedly moving rapidly to indict him, which would move the case up to county court.With reporting by Taylor K. Vecsey