YouTube shooting: U.S. female mass shooters are a rare occurrence

On Tuesday, a woman opened fire at YouTube headquarters in the San Francisco area. Three people were injured before the woman appeared to take her own life.

Many people’s eyebrows were raised when they found out the shooter was female, illustrating how rare an occurrence it is.

A New York Police Department report on active shooters stated that only eight of 230 cases between 1966 to 2012 involved female attackers.

READ MORE: Female suspect dead after shooting at YouTube HQ left at least 3 injured

There are many incidents in the U.S. each year similar to what happened in California on Tuesday, but few are recognized as “mass shootings” including this one.

The FBI definition of a mass shooting is when four or more people are killed indiscriminately by a shooter.

Female mass killers are “so rare that it just hasn’t been studied,” James Garbarino, a psychologist at Loyola University Chicago, told Haarper’s Bazaar.

WATCH: People evacuate YouTube HQ during active shooter situation

0:50 People evacuate YouTube HQ during active shooter situation

Between 1982 and February of this year, there have been 96 mass shootings in the United States, according to Statista.

Of those 96 shootings, there were two committed by women, and one other case where a man and woman were both involved.

The latter case occurred in San Bernardino, Calif., in December 2015, when Syed Rizwan Farook and Tashfeen Malik opened fire at a community centre. Fourteen people were killed and 22 others were left injured.

1:24 Massive police presence at YouTube HQ in California for reports of active shooter

• Massive police presence at YouTube HQ in California for reports of active shooter
• People evacuate YouTube HQ during active shooter situation
• Police pat down people outside YouTube HQ during active shooter
• Police patrol grounds of YouTube HQ during active shooter situation
• Police say suspect believed to be YouTube HQ shooter dead, at least 3 people injured

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In 2014, Cherie Lash Rhoades killed four people and wounded two others in a gun and knife attack in Cedarville Rancheria, Calif.

In 2006, Jennifer San Marco shot and killed seven people at a postal facility in Goleta, Calif., before taking her own life.

The homicide statistics also paint a similar picture as around 10 to 13 per cent of murders in the U.S. are committed by women, according to a report cited by Live Science.

Adam Lankford, author of The Myth of Martyrdom: What Really Drives Suicide Bombers, Rampage Shooters, and Other Self-Destructive Killers told the website that the number falls to eight per cent when the act involves guns.