This is an example of voluntary manslaughter.
Some American states call this crime a third-degree murder, although generally it is known as voluntary manslaughter. It happens when a person didn't plan on murdering anyone, but happened so in a fit of anger, for example. An example of such a crime would be if a husband came home and saw his wife cheating on him with another man, and he kills one or both of them in the heat of passion.
