Now Playing: US-backed forces officially declare victory in Raqqa
Now Playing: US commander congratulates Syrian Democratic Forces on liberation of Raqqa
Now Playing: Drone footage shows widespread Raqqa destruction
Now Playing: Questions remain 2 weeks after deadly ambush in Niger
Now Playing: Pilots perform risky honor lap stunt, alarming travelers in terminal
Now Playing: Austrian hotel helps refugees gain work experience
Now Playing: Investigators: Russian trolls set up fake groups to organize real activists
Now Playing: Pilots suspended after mid-air stunt with 200 passengers
Now Playing: Air Berlin pilot performs low fly-by
Now Playing: Major milestone in war against ISIS
Now Playing: Drone soars over Raqqa, shows flattened, crumbling buildings
Now Playing: Former street violin performer awarded music school scholarship
Now Playing: Site of ISIS beheadings in Raqqa seized by Kurdish-led force
Now Playing: Sebastian Kurz: Everything you need to know
Now Playing: Chinese citizens share their thoughts on President Xi Jinping
Now Playing: Xi Jinping: China’s strongest leader in generations
Now Playing: Drone video shows Rohingya exodus continues unabated
Now Playing: Freed hostages settle in Canada after release from Taliban captivity
Now Playing: US father of 3 killed in Somalia was refugee who arrived there hours before attack
Now Playing: Rescued hostage Joshua Boyle says children are ‘improving’
