Why California shooting is rare among US mass shootings

The deadly California mass shooting that left 14 people killed and 17 others injured marked the 355th mass shooting in the US in less than as many days in 2015, experts report.

As more details are yet to emerge regarding the gun violence at a holiday party, it is clear that these types of crimes are morphing and not abating.

"Shootings involving mission-oriented females may be a new threshold which should be concerning to all of us and the incident in San Bernardino might just be a hybrid, and a harbinger, of shootings to come," said Mary Ellen O'Toole, director of forensic science programme at George Mason University.

A "hybrid" means a spinoff from other cases of mass murder.

"Like a cancer, this crime is moving and growing in insidious ways, and is resistant to 'treatment'," Dr O'Toole added.

As described in the article titled "The Mission-Oriented Shooter: A New Type of Mass Killer" published in the journal Violence and Gender, a mission-oriented shooter is a person whose mission is to kill as many people as possible, or to achieve maximum lethality.

These particular crimes are well planned and can involve months and even years of preparation.

In contrast to more recent mass shootings, the one that took place in San Bernardino is the first since Columbine high school shooting to involve more than one of these types of shooters and, perhaps more surprisingly, the first to have involved a female shooter.

"Guns, clearly, are the elephant in the room but from a behavioral perspective, the 'character' and morality of people in this country appears to be seriously degrading," Dr O'Toole noted.

"The lack of compassion, lack of guilt and empathy, an embrace of violence as a method to handle world problems, and a generalised world hatred push those people towards guns to carry out their desire for human destruction," the author wrote.

According to Jeremy Richman, director of the Avielle Foundation that publishes Violence and Gender journal, we must push for brain health advocacy and research as we are all responsible for meaningful change.