While official cause of Riley's death is still unconfirmed, Tootsie Iovine, a family friend, said that the singer took his life and was found on Friday in the basement of the apartment he was staying in, reported Aceshowbiz.
His friend and fellow Philadelphia busker Robby Parsons confirmed the news to Yahoo! Music.
"Anthony passed away Tuesday. His sister called me to tell me...I called the friend he'd been living with, Bobby Iovine, and Bobby was in tears," Robbie said.
His sister said the family had not finalised funeral arrangements but confirmed a public memorial.
Riley left "The Voice" season 8 before the Knockout Rounds over "personal reasons," apparently to deal with substance abuse issues. He then returned to Philadelphia to enter rehab.