It is likely suicide. In time, as the official investigation continues, Walter has to admit to a couple of questionable activitiesstalking Clara's bus in his car, while daydreaming about possibly killing her at the first stop and visiting Melchior Kimmel, a bookshop manager who got away with killing his own wife, prior to Clara's death.
The situation is likely fatal. As the official investigation continues, Walter has to admit to some questionable actions, including following Clara's bus in his car while daydreaming about killing her at the first stop and visiting Melchior Kimmel, a bookshop manager who killed his wife before Clara's death.