Now Playing: Ominous war of words continue between Trump and North Korea's leader

Now Playing: McCain says he will vote 'no' on the latest attempt to kill Obamacare

Now Playing: Thousands in Puerto Rico are told to evacuate as a new disaster unfolds

Now Playing: Rescue efforts continue after devastating earthquake in Mexico City

Now Playing: Walmart tests out a new grocery delivery service

Now Playing: 4-legged hero amongst the first responders in Mexico City

Now Playing: Hostage situation unfolding at a bank in Tennessee

Now Playing: New images of rescued survivors of the earthquake in Mexico City

Now Playing: Trump announces a new round of sanctions against North Korea

Now Playing: Senate has a little over a week to repeal Obamacare

Now Playing: Thousands of people in Puerto Rico face an uncertain future

Now Playing: On the island of Dominica, nearly complete destruction by Hurricane Maria

Now Playing: Mark Zuckerberg promises Facebook will step up efforts to fight election interference

Now Playing: Surveillance video captures mystery house explosion in California

Now Playing: Fiery car rescue in Atlanta

Now Playing: Questions arise after police shooting of a deaf man in Oklahoma City

Now Playing: A new tradition in college sports

Now Playing: Index: California dad and children struck by lightning

Now Playing: 8-year-old meets his bone marrow donor for the 1st time

Now Playing: Investigators interview Rod Rosenstein as part of Russia probe