A grim national record has been set in Orlando, Florida, the deadliest mass shooting in US history.

It's being investigated as an act of terrorism.

Every time there's a terrorist attack, we ask ourselves, what could motivate someone to

commit mass murder?

Although it's still early in the investigation, we know enough to say that this was an act

of terror and an act of hate.

Officials say 29-year-old Omar Matin called 911 to pledge allegiance to the Islamic

State during his rampage inside the Pulse, a gay nightclub in Orlando.

Was he motivated by religious fervor, by homophobia, by both?

I remember asking similar questions after the shooting in San Bernardino last year.

Many people first thought that a disgruntled employee was behind that attack.

Later, we learned the killers had pledged allegiance to the Islamic State.

The truth is, we may never fully understand.

Some terrorists may be motivated solely by religious fervor.

Others might be cloaking personal grievances in the garb of something grander.

In fact, capitalizing on the personal frustrations of potential recruits is an explicit strategy

of the Islamic State, according to anthropologist Kart Atron, who has studied the group.

The strategy of the Islamic State is quite simple and very well spelled out.

We will find out who in our enemy populations have grievances, have frustrated personal aspirations.

We will draw that out and we will wed it to the story we have of how the world should

change and why.

This week, we will share an episode we ran some months ago about why young people turn

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