Udo is the mentally unstable child of the Bricks family. Late in the story we find out that he is responsible for the death of Fabrizius. Udo incorrectly assumed that when Elvira Bricks, his mother, told him to get rid of Fabrizius, that she meant for him to kill him. This is by no fault Udo's mistake as he didn't know any better. After all....look at the poor kid.