mass shooters who murdered someone for mercy

Mass shooters/failed mass shooters who killed one or more of their victims for "mercy" or something similar.

Mutsuo Toi:  killed her grandmother because he couldn't bear to let her live and face the shame and social stigma that being the grandmother of a "murderer" would bring.

Sidnei Ramis de Araujo: He killed his son, because he couldnt let his son suffer the murder of his family, and living knowing that his father is a murder

Charles Whitman indicated in his notes that he killed his mother and wife to spare them future humiliation and suffering.