Mascherino, or Father Al to those who knew him, had been diagnosed with cancer and recently told those close to him he wasn't long for this life. He died Friday. He urged those also involved in the effort to create and maintain the 9/11 memorial chapel to carry on with his work, the Pittsburgh Tribune-Review said Tuesday.
Archbishop Ramzi Musallam, of the Catholic Church of the East, will now oversee the chapel.
"He trusted in me to continue his work," Musallam said. "I thank God for his trust and his love as a brother. He asked for me to keep the dream, to keep those heroes here on the mountain alive."
United 93 crashed in a field in Shanksville, Pa., after hijackers tried to overtake the flight but the 40 passengers on board resisted.
Mascherino oversaw the purchase and renovation of a small former Lutheran church near the crash site, converting it into a non-denominational chapel and memorial site.
Mascherino is a bishop in an offshoot branch of Catholicism, North American Old Roman Catholic Church, Utrecht Succession, which does not recognize the authority of the pope.