FLAGSTAFF, Ariz. -- A criminal justice professor said familicide, a crime in which a parent kills his or her family, is on the rise.

"We've noticed over the past year a marked increase in familicides nationally," said Neil Websdale, a professor at Northern Arizona University.

Websdale believes the recession is one of the reasons behind the spike.

"I think what's happening is perpetrators are killing because they somehow perceive that they have failed as providers, lovers, fathers, and in a small number of cases, wives and mothers," he said.

Websdale just wrote the book Familicidal Hearts, which will be released in January. In the book, he looked at 211 cases of familicide. In 196 of those cases, the father was the killer.

Websdale said the recent murder-suicide in Mesa where a mother apparently killed her two teenage sons before killing herself is the exception to the rule.

"Without knowing all the facts, it's tough to say what was behind it -- but it definitely looks like a rare case," he said.