Familicide

[6] Sippenhaft (English: kin liability) was used in Nazi Germany to punish and sometimes execute the relatives of defectors and anyone involved in the 20 July plot.

[7] La Cosa Nostra began killing the relatives, including women and more recently children, of informants (pentiti) and rivals in the 1980s.

[10] According to ABC News contributor and former FBI agent Brad Garrett, people responsible for killing their families tend to be white males in their 30s.

[12] In Australia, a study was done of seven cases of familicide followed by suicide in which marital separation followed by custody and access disputes were identified as an issue.

Some common factors such as marital discord, unhappiness, domestic violence, sexual abuse, threats of harm to self or others were found in varying degrees.

[16] Far fewer women commit familicide, and those who do usually have different reasons, including perceived or imagined loss of custody of children.

Lastly this article reported two studies, one of which found that many of the motives involved feelings of abandonment, psychosis, and narcissistic rage.