What is the purpose I'd killing the pig and leaving the bloody ax?

Taking advantage of Pap's absence, Huck quickly finishes his sawing and climbs out of the cabin, taking everything worth any money to his canoe. He axes down the front door and goes hunting for game. Huck shoots a wild pig, butchers it inside the cabin, and spreads the blood on his shirt and the floor. He also carefully lays some of his hairs on the now bloody ax to make it appear as if he has been killed. Huck cuts open a sack of flour and marks a trail indicating that the killer left via a lake that does not connect to the river. Thus, he prevents anyone from searching along the river for anything more than his dead body.