Watch: Esteban Santiago, Suspect in Fort Lauderdale Attack

He is the alleged perpetrator of a shooting spree that left five people dead and more injured in the Fort Lauderdale airport this afternoon.

But tonight, Esteban Santiago remains a mystery for federal authorities who are trying to piece together just what led a 26-year-old Army veteran with an intense gaze to go on a murderous rampage.

As he sits in detention – after apparently turning himself over to police without a fight – his social media accounts are providing authorities with early clues.