A "family annihilator" is someone who kills more than one member of his family, and we write "his" because these killers happen to be overwhelmingly male.
While that may not be terribly surprising, researchers also found another odd commonality after studying patterns in 71 cases. According to a study published in the Howard Journal of Criminal Justice, a disproportionate number of the killings happened in the month of August, and more than half on weekends. To get even more granular, most of the killings happened on Sundays.
So the obvious question is why?
Data tells the story. In two-thirds of the cases, family disputes like access to children triggered the killings. These disputes tended to blow up around the time that fathers had to return children to their mothers, and this happens most often on Sundays.