Homicide is justifiable when committed by public officers and those acting by their command in their aid and assistance, either—
1. In obedience to any judgment of a competent Court; or,
2. When necessarily committed in overcoming actual resistance to the execution of some legal process, or in the discharge of any other legal duty; or,
3. When necessarily committed in retaking felons who have been rescued or have escaped, or when necessarily committed in arresting persons charged with felony, and who are fleeing from justice or resisting such arrest.