Homicide is excusable in the following cases:
1. When committed by accident and misfortune in doing any lawful act, by lawful means, with usual and ordinary caution, and without any unlawful intent.
2. When committed by accident and misfortune in the heat of passion, upon any sudden and sufficient provocation, or upon a sudden combat provided that no undue advantage is taken, nor any dangerous weapon used, and that the killing is not done in a cruel or unusual manner.