On Tuesday, Nasim Aghdam injured three people before killing herself at YouTube's Northern California headquarters. Investigators now say the shooter's motive was probably anger toward YouTube, which fits a common FBI profile. Almost half of the country's active shooter incidents take place at businesses.
But one thing about Aghdam stands out that makes her unique among mass shooters. She was a woman. Eric Madfis is a professor of criminal justice at the University of Washington at Tacoma. He said that 94 to 96 percent of mass shooters are male, depending on which measurement is being used.
Of course, no blanket statements can be made, but Madfis said the reason there are many more male mass shooters is generally connected to the different ways men and women process negative life events.
It's the case that by and large men are more likely to externalize blame, as opposed to women who are much more likely to internalize blame and see the problems as being caused by their own deficiencies and things like that, as opposed to externalizing it and [having] it lead to violence in that way.
Madfis said the lack of female mass shooters makes it hard to study the group conclusively, but when looking at murders in general, some trends indicate where male and female killers differ.
Men are much more likely to use firearms, that's true. Women are much more likely to use poison and things like that. And part of it also does have to do with the fact that men are more likely to have access to weapons. They're more likely to have had extensive training in the use of firearms. So that makes a difference not only when they do these things but also in how many people they kill when they commit and attack. It is true that male mass shooters tend to kill more people than women do on average.
There are some unifying factors among many mass shooters, both men and women, Madfis said. Most have had a series of setbacks or failures in their life, what Madfis calls 'cumulative strain.' In many cases there is an inciting event just before the shooting is committed. They also often target a place that is symbolic in some way, which seems to be true of the YouTube shooting too, he said.
Madfis said there are some myths about mass shooters as well. Most do not plan their attacks overnight, and although some have mental health problems, that is not a universal characteristic.