So he goes out in the forest and starts to whistle to see if something will come out of the woods.
The Headless Horseman of Sleepy Hallow supposedly passes Ichabod. Ichabod is really bad at riding the horse and falls off the horse, but the Headless Horseman is known to throw his pumpkin head at his victims, and that is what he does.
After the passing of the Headless Horseman, Ichabod was never seen again. He most likely just ran away, but people in the town found an abandon horse with a saddle on. The people of the town more or less think that the horseman killed him.
Ichabod will never return to Sleepy Hallow again, and people would wonder where oh where he went. They will never really know though.