Motives behind mass violence can be a complex mix

WASHINGTON -- Why did they do it?

The California rampage that left 14 dead shows the motives behind mass violence can be complex and difficult to determine. The careful planning, multiple shooters and military-style weapons seem to match up with recent terror attacks. But other circumstances -- killing people known to an attacker, for example -- may be more in line with the deep anger and personal frustration of a workplace assault.

Pinpointing a motive can be that much harder when a suspect commits suicide or is killed without leaving behind a manifesto detailing ideological views or personal grievances.

Federal authorities still are exploring the reasons for Wednesday's mass shooting at a San Bernardino, California, social-services center. Police say the two suspects, Syed Rizwan Farook, a 28-year-old county restaurant inspector, and his wife, Tashfeen Malik, 27, were killed later in a shootout with officers.

The FBI said it's exploring possible motives, including terrorism or workplace violence. President Barack Obama said Thursday it was "possible this was terrorist-related," but authorities were unsure. He also raised the possibility it was a workplace dispute or mixed motives were at play.

"What happened doesn't fit the standard model for either, and that's one of the things that makes it more confusing," said Mark Pitcavage, an extremism expert at the Anti-Defamation League.

"The idea of two people participating in a workplace-violence shooting, that's just very rare," he added. "On the other hand, if this was ideologically motivated, the target that was chosen is such an unusual target."

It's not uncommon for acts of extreme violence to be driven by mixed or confusing motives, particularly in an era of pervasive social media, when groups such as the Islamic State can blast out public exhortations and reach an audience of the disaffected and angry easily.

"I think what we have to come to grips with in America is that this is no longer a neat package," said Erroll G. Southers, a former FBI agent who is director of Homegrown Violent Extremism Studies at the University of Southern California. "That when these things happen, even as we're trying to determine whether or not it's terrorism, that we can simply say it's 'a' or 'b,' when in fact it could be a mix of both."

David Gomez, a former FBI national-security and criminal profiler, said, "It's very rare that something is only a sexual homicide or an anger-driven homicide or financial, because it all interweaves. People always want to make a call very early on in the investigation, which is extremely hard to do."