murder is where one person wrongfully kills another person with malicious aforethought. if a person does something reckless that makes someone else die, without the intention of killing, it is homicide and may be manslaughter. an accident caused by carelessness may be criminally negligent homicide. sometimes, a death caused by someone else may not be a crime, for example killing in self-defense. though, if the killer could've stopped a violent encounter without killing the victim, it's generally "not" a lawful killing.