Now Playing: Chicago Train Derailment Injures at Least 32 People

Now Playing: US authorities warn about possible homegrown attack with acid

Now Playing: Stevie Wonder, Green Day and more play Central Park for Global Citizen festival

Now Playing: Prince Harry kicks off Invictus Games in Toronto

Now Playing: Athletes, fans divided over Trump's Kaepernick comments

Now Playing: Tensions between US and North Korea deepen after UN speech

Now Playing: Trump takes on NBA and NFL stars

Now Playing: History of social activism through sports

Now Playing: Residents of Puerto Rico facing long recovery after Hurricane Maria

Now Playing: Earthquake reported in North Korea near site of recent nuclear test

Now Playing: Drone collides with Black Hawk helicopter

Now Playing: Plane makes crash landing on California street

Now Playing: Syrian-American journalist and her mother killed in Turkey

Now Playing: Treasury secretary under investigation for private plane use

Now Playing: ESPN's College Game Day comes to Times Square

Now Playing: Nursing home worker not giving up on her patients

Now Playing: Trump campaigns for Alabama senator in GOP election fight

Now Playing: 'Star Wars: Last Jedi' officially wraps

Now Playing: Death toll rises to nearly 300 from Mexico City quake

Now Playing: Puerto Rico, still without power after Hurricane Maria, now at risk of dam failure