And we've come inside for a moment here in dallas, to tell you more about the investigation speeding ahead at full tilt. The suspect remains in the hospital. His every word and facial expression has... See More
And we've come inside for a moment here in dallas, to tell you more about the investigation speeding ahead at full tilt. The suspect remains in the hospital. His every word and facial expression has been analyzed and scrutinized by a team of expert. And abc's brian ross tells us now what they're learning about his motivation, his inspiration. Reporter: With the injuries to his head, neck, legs and hand healing, the hospital today upgraded the condition of dzhokhar tsarnaev from serious to fair. So far the only word he has spoken is a grunted no. At the same time, friends sought to upgrade image. One posted this undated video on youtube, showing dzhokhar doing the robot dance with buddies on the wrestling team. Hardly the anti-american islamic radical accused of following his brother in bombing the mar it does appear the elder brother was the driving force, that he was very angry at u.S. Foreign policy. Reporter: The younger brother told the fbi that he and his brother were inspired by the anti-u.S. Internet preaching of the radical cleric anwar al awlaki. Even though the american born al qaeda figure was killed in a -- more than a year and a half ago, his words still have power. Here condemning the u.S. Actions in iraq and afghanistan, which the younger brother said, became their motivation to attack. We have chosen the path of war in order to defend ourselves from your oppression. Reporter: The elder brother tamerlan had another favorite speaker. A chechen rebel leader threatening death to anyone who helps the infidels. He was killed by the russians last year. And it was on the internet, dzhokhar told fbi agency -- agents that they learned how to make a bomb with a pressure cooker. Reporter: In russia today, the mother of the brothers tsarnaev, who first encouraged her older son. Reporter: In her first on-camera interview, said her sons were being set up. What happened is a terrible thing, but I know that my kids have nothing to do with this. I know it, I am mother. The parents are talking about coming to boston to see their surviving son and claim the body of the dead one. If the mother comes, she could face arrest for failing to show up in court in boston last year, on charges she shoplifted $1,600 worth of clothes at the lord & taylor departmenore there, diane? Brian, thanks so much.
This transcript has been automatically generated and may not be 100% accurate.