Now Playing: ABC News Live Update: Johnson & Johnson vaccine gets emergency use authorization

Now Playing: Connecticut man arrested for throwing Molotov cocktails at 4 ambulance facilities

Now Playing: Flooding sparks rescues, evacuations for seniors

Now Playing: Third COVID vaccine ships out today

Now Playing: Police investigating fraternity pledge death

Now Playing: Severe weather across the Southeast

Now Playing: Doctor under fire for attending virtual court from operating room

Now Playing: Tiger Woods breaks silence after crash

Now Playing: Biden's COVID-19 relief package faces tough road in Senate

Now Playing: Heavy downpour causes flash flooding in Tennessee

Now Playing: 2nd woman accuses New York governor of sexual harassment

Now Playing: Johnson & Johnson CEO on COVID-19 vaccine approval and rollout

Now Playing: Details emerge in death of Ronald Greene

Now Playing: Manhole catches fire and explodes in NYC

Now Playing: 2nd woman reportedly comes forward against New York governor

Now Playing: Trump makes 1st major address since leaving office

Now Playing: John Legend discusses his response to George Floyd's death

Now Playing: Snow and flood threats across Eastern US

Now Playing: '(Biden) missed opportunity to rethink the alliance' with Saudi Arabia: Fred Hiatt

Now Playing: '(We're) really grateful that we have 3 really efficacious vaccines': Dr. Fauci