Now Playing: Mikaela Shiffrin : 'it's a lot of dedication. It's pretty much a 24/7 job.'

Now Playing: Teen arrested in murder of transgender woman

Now Playing: US military says Chinese warship nearly collided with a Navy destroyer

Now Playing: Texas shooting leaves 1 dead, 4 injured

Now Playing: Michael Waldman talks about new book 'Supermajority'

Now Playing: Maren Morris joins Taylor Swift onstage during Chicago stop of Eras Tour

Now Playing: New warnings for tourists about wildlife at Yellowstone National Park

Now Playing: A look at what's in the new debt deal

Now Playing: Joran van der Sloot to be extradited to US

Now Playing: OPEC announces global oil supply cut just in time for summer

Now Playing: Plane with unresponsive pilot crashes, killing all 4 aboard

Now Playing: Concerns of West Coast port disruptions amid contract talks

Now Playing: Sonic boom that rattled Washington, DC, caused by military jets

Now Playing: 13-year-old looking to make golf history

Now Playing: New York to propose legislation criminalizing printing ghost guns at home

Now Playing: Canadian fires bring dangerous air quality to the US

Now Playing: Body of missing resident in collapsed Iowa building found, officials say

Now Playing: 2 massive fires started by lightning

Now Playing: Paralyzed teen excels in sports

Now Playing: Mother leaves 2 kids in car that caught fire while allegedly shoplifting: Police