Harry and Voldemort were facing each other for the final time, about to begin a duel for their lives. Voldemort, it turned out, had had Ollivander make a new wand for him so he and Harry could duel properly.
"Tonight," said Voldemort, "is the night that you leave this earth, Harry! Are you prepared to face death?" He laughed.
"As long as you're defeated," Harry said valiantly, "then I don't care if I die!"
They began to duel, each of them casting many Shield Charms and Unforgivable Curses at each other.
Voldemort shouted, "EXPELLIARMUS!" and Harry's wand flew across the room in which they were dueling. Harry scrambled for it, and once he reached his wand, he turned around and pointed it directly at the now mortal Voldemort. He screamed. "AVADA KEDAVRA!"
Unforunately for Harry, in all the confusion of the duel, he had picked up his wand backwards, and a jet of green light zapped Harry right in his heart.
As Harry crumpled to the floor, Voldemort walked over to him, picked up Harry's wand, and said, "Huh. What were the odds of that?"