Heckner was born in Munich. He trained as an actor with Peter Rieckmann, at the Kreide Theatre in Munich. In 1978 held a novice engagement at Coburg State Theatre. After he graduated, he began to appear in films. In 1979 he got his first role in "The wonderful years" by Franz Seitz and Rudolf Noelte. His biggest roles, are in Downfall, where he played Walter Wagner, the man who wed Hitler to Eva Braun and in Sophie Scholl - The Final Days, where he portrayed Dr. Wüst. He also starred in many TV productions, such as Tatort, For Heaven's Sake and many others.