teixeira. >> jack douglas teixeira. >> jack teixeira. >> the man suspected of leaking highly classifieds been found. >> that's him in the red shorts there. >> the 21-year-old massachusetts air national guard member was takeinto custody earlier today. ♪ ♪ (helicopter blades churning) >> this 21-year-old air national guard member is alleged to have disclosed hundreds of top-secret government documents online to his gaming buddies. >> why did he do it? how did he do it? what drove him? who is he? >> narrator: over the next six months, reporters at "the washington post" would investigate jack teixeira's world. it largely played out online. >> our whole team was working on this, creating networks, basically, of people, based their social media profiles, because they interacted in some way with jack or someone he was connected to. >> narrator: chris dehghanpoor specializes in tracking down sources online. he worked as an information security engineer at a gaming platform before becoming an investigative reporter at the "post." ♪ ♪ >> the first thing i tried to do was to find a steam profile.

(helicopter blades churning) >> jack teixeira. >> jack douglas teixeira. >> jack teixeira. >> the mang highly classified military documents has been found. >> that's him in the red shorts there. >> the 21-year-old massachusetts air national guard member was taken into custody earlier today. ♪ ♪ (helicopter blades churning) >> this 21-year-old air national guard member is alleged to have disclosed hundreds of top-secret government documents online to his gaming buddies. >> why did he do it? how did he do it? what drove him? who is he? >> narrator: over the next six months, reporters at "the washington post" would investigate jack teixeira's world. it largely played out online. >> our whole team was working on this, creating networks, basically, of people, based their social media profiles, because they interacted in some way with jack or someone he was connected to. >> narrator: chris dehghanpoor specializes in tracking down sources online. he worked as an information security engineer at a gaming platform before becoming an investigative reporter at the "post." ♪ ♪ >> the first thing