'Manslaughter' in the Bible

Someone could flee there who committed manslaughter, killing his neighbor accidentally without previously hating him. He could flee to one of these cities and stay alive:

You are to determine the distances and divide the land the Lord your God is granting you as an inheritance into three regions, so that anyone who commits manslaughter can flee to these cities.

Otherwise, the avenger of blood in the heat of his anger might pursue the one who committed manslaughter, overtake him because the distance is great, and strike him dead. Yet he did not deserve to die, since he did not previously hate his neighbor.