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 when no undue advantage is taken nor any dangerous weapon used, and when the killing is not done in a cruel or unusual manner.