It wasn't the economy. It wasn't stress. It wasn't mental illness.
It hit me the minute I heard the news - it was ownership.
When William Parente beat and suffocated his wife and two daughters before taking his own life, it wasn't just because his shaky financial dealings were about to come crashing down on him.
And when Christopher Wood killed his wife and three children and then himself, it wasn't just because he was $460,000 in debt and depressed.
Financial disaster was looming for both men, and both were undoubtedly under terrible strain. But they didn't do what Freddie Mac executive David Kellermann did, which was to take his own life and allow his wife and young daughter to survive.
Wood and Parente felt entitled to make a decision for their family members that they would be better off dead than shamed or homeless or simply poorer. These homicides were proprietary as well as protective.
"The men who commit this kind of familicide have almost no track record of domestic violence or child abuse," said Dr. Richard Gelles, dean of the University of Pennsylvania School of Social Policy and Practice and an expert on family violence.
"In fact, these kinds of men are probably over-enmeshed with their families. They don't see any boundaries between their lives and their wives and children. And a good deal of their identity is wrapped around being the husband and the breadwinner."
In family relationships, there is a toxic kind of patriarchy, in which the man views his wife and children as possessions, and believes it is his right to treat them any way he wishes - even to hit and abuse them.
This is the kind of "If I can't have her, nobody will," patriarchy that can also result in murder, according to Rethinking Violence Against Women, a textbook on domestic violence edited by Rebecca Emerson Dobash and Russell P. Dobash.
But the kind of subtle patriarchy that may have been operating in Wood and Parente appears to have been just as deadly.
This patriarch sees the family as a whole, a unit, and he believes he is entitled to decide the fate of that unit. When disaster approaches, he believes he is rescuing his family from suffering, according to the researchers in Rethinking Violence Against Women.
The authors suggest that this kind of violence is not "mindless, incomprehensible, unpredictable behavior by an alcoholic, mentally unstable or socially desperate" man.
This violence can be "functional, intentional and patterned."
In fact, Wood and Parente, if they could speak to us, might defend their actions by saying their wives and children couldn't cope without them, that killing them was a mercy.
I asked Gelles if the root of Wood's and Parente's actions might be found in the lingering legacy of English law in which a man's wife and children become his property. He agreed.
"There is a long cultural history there," said Gelles. "... The cultural DNA that makes women and children the property of the man is still in the gene pool."
What happened to these two families is a tragedy. But it is not simply the result of economic strain or mental illness. And it wasn't random craziness or a lightning strike.
Beneath the exterior of these model fathers were men who believe they had the right and the obligation to make all the family decisions, including those of life and death.
It might never have occurred to William Parente to ask his daughter Stephanie, a much-loved Loyola College student, if she would rather live with the shame and financial devastation he was about to bring upon the family, or if she would rather die.