A new study of “family annihilators” -- people who murder their own kin -- finds that most are men whose motivations differ from those of serial or spree killers.

The study was led by researchers from the Birmingham City University’s Center of Applied Criminology in England. Based on the team’s research, the study was able to classify family killers into four types: anomic, disappointed, paranoid and self- righteous.

Anomic killers have an economic motivation. Family equals economic success to this group, and the crime occurs as a result of the father losing his job, or facing financial hardship. The family no longer has value as a sort of trophy, says David Wilson, the center’s director. A self-righteous killer blames the mother for his crime, citing her failure to properly raise the family. The disappointed killer believes the family is not living up to his standard, ideals or beliefs. And the paranoid killer thinks he is trying to protect his family, fearing someone or some agency is trying to take his children away.

According to Wilson, individuals who murder their families may be improperly categorized as serial or spree killers despite differences in their motives and backgrounds. He said in a statement, “Often they are treated like spree or serial murderers, a view which presupposes traits, such as the idea that the murderer 'snaps,' or that after killing their partner or children the killer may force a standoff with the police.”

To properly classify these family annihilators, researchers studied 30 years of cases, 71 in total, and discovered several characteristics of these killers. The murderer in 59 of the cases was male and this type of crime has increased over the course of the study period, with the majority occurring in the 21st century. “We also found that the rate at which this type of crime is being committed has increased, with the first decade of the 21st century claiming over half of all cases,” said Wilson.

Of the male murderers, the majority, 55 percent, were in their 30s while only 10 percent were committed by men in their 20s. According to the study, the murder of a family by a father was more common over the weekend, and 20 percent of all cases occurred in August. Wilson said the timing may be due to the father not having to go to work while adding, “There may also be a symbolic factor as estranged fathers know that by the end of the weekend they will have to hand their children back to the mother.”

The study discovered another important distinction between spree killers and family killers. Of family killers, 81 percent attempted to commit suicide and there were no reports of a standoff with police, an aspect typically associated with spree killings.

Other statistics from the study revealed 71 percent of family killers were employed at the time of the crime, the most common murder methods were carbon monoxide gassing and stabbing, and the crime was most likely to occur at home.

The four types of killers are all motivated by a concept of masculinity, notes Wilson, and the murder acts as a final attempt to restore order or the role of the father. Wilson concludes that family killers should be classified differently from serial or spree killers and understanding gender, and concepts of gender or family roles, could help explain why the frequency of this type of crime has increased in recent years. The study will be published in The Howard Journal of Criminal Justice.