A battalion chief who had been considered a rising star in the Fire Department of New York was killed Tuesday when a row house exploded as he was supervising an evacuation following a report of a gas leak, and authorities are looking into whether the building was being used to grow marijuana. Later Tuesday, investigators said they were questioning a person of interest but provided no details. The two-story house and adjoining homes in the Bronx had already been emptied of occupants and fire personnel had been on the scene for an hour when the 7:30 a.m. blast jolted neighbors awake, tore off the building’s roof and hurled pieces of wood and brick into the street.