Such homicide is manslaughter in the first degree when committed without a design to effect death, either 1. By a person engaged in committing or attempting to commit a misdemeanor, affecting the person or property, either of the person killed, or of another; or 2. In the heat of passion, but in a cruel and unusual manner, or by means of a dangerous weapon; 3. By shooting another with a gun, or other firearm when resulting from carelessness in mistaking the person shot for a deer or other animal.