His body was found on Friday night, according to The Hollywood Reporter.
Polish police are currently investigating the death, according to family friend and publicist Jim Dobson.
"We are all deeply shocked and saddened at the news of the sudden death of Marcin Wrona," the Toronto Film Festival said in a statement.
"His film 'Demon' truly marked the emergence of a strong new voice on the world cinema stage. Our thoughts go out to his friends and family, especially his wife and producing partner, Olga Szymanska, who was with him at the premiere in Toronto."
He directed two other films prior to "Demon" -- 2009's "Moja Krew" ('My Flesh My Blood') and 2010's "Chrzest" ('The Christening'). He was considered one of the rising stars in the Polish film industry.
He was also a lecturer at the Radio and Television Department of the University of Silesia in Katowice.
Wrona is survived by his newlywed wife, Olga Szymanska, who was a producer on "Demon".
