Terrorist Attacks Why It's So Hard to Track a 'Lone Wolf'

So-called "lone wolf" terrorists, like the man behind the mass shooting at the Pulse Nightclub in Orlando, are difficult for authorities to monitor -- but Trump's anti-immigrant rhetoric is no solution.
Von Peter Bergen
An undated photo from a social media account of Omar Mateen, who killed 49 people in the mass shooting at Orlando's Pulse nightclub.

An undated photo from a social media account of Omar Mateen, who killed 49 people in the mass shooting at Orlando's Pulse nightclub.

Foto: HANDOUT/ REUTERS