WATCH: Group encounters bison at Yellowstone National Park

  • Now Playing: Tour group surrounded by herd of bison

  • Now Playing: Bison walks through snowstorm in Yellowstone National Park

  • Now Playing: Nearly 500,000 Americans have died from the coronavirus

  • Now Playing: New information released regarding the death of Malcolm X

  • Now Playing: Biden administration works to get vaccine rollout back on track

  • Now Playing: Is the new stimulus package likely to pass?

  • Now Playing: FEMA administrator speaks out on Texas homeowners, renters filing for assistance

  • Now Playing: Many Texans report high utility bills after power outage

  • Now Playing: United Airlines plane part narrowly misses homes after engine failure

  • Now Playing: Debate intensifies over reopening public schools

  • Now Playing: Carjacking suspect taken down in Philadelphia

  • Now Playing: Texas declared major disaster zone

  • Now Playing: Plane conducts emergency landing after dropping debris in Colorado

  • Now Playing: Boy rescued from frozen pond in Texas

  • Now Playing: Stranger shovels out resident’s driveway

  • Now Playing: Milder temperatures to move into southern US

  • Now Playing: Massive fire breaks out in Texas hotel

  • Now Playing: Man who allegedly attacked Chinese woman on NY street arrested

  • Now Playing: Spectacular images sent from Perseverance rover on Mars

  • Now Playing: 6 United Airlines pilots breaking color barrier in predominately white industry