Now Playing: PREVIEW: Sharia Law

Now Playing: REPORTER'S NOTEBOOK: Islam in China

Now Playing: 'Bipartisan consensus that James Comey doesn't have credibility': Sarah Sanders

Now Playing: Obama, Comey made 'similar mistake' presuming outcome of 2016 election: Top House Dem

Now Playing: Comey 'violated... FBI's own guidelines' with leak, but didn't break law: GOP senator

Now Playing: U.S. and allies strike Syria; Trump lashes out against Comey, Cohen raids on Twitter

Now Playing: Foreign policy experts: Tensions with Russia the highest they have ever been

Now Playing: Chris Christie: EPA's Pruitt 'should have never been there in the first place'

Now Playing: GOP retirements could lead to openings for House Democrats

Now Playing: Sen. Dem: For legislation to end gun violence, put 'far right, far left rhetoric aside'

Now Playing: Young protesters will be part of 'redemption of America': Friend of MLK Jr.

Now Playing: If Trump doesn't 'follow through' on Syria tweet he risks looking 'weak': Sen. Graham

Now Playing: Increase in border crossings is 'alarming': White House homeland security adviser

Now Playing: Farmers in Iowa talk about fear factor of tariff threats from China

Now Playing: Trump can replace EPA chief with someone who has no 'baggage': NPR host

Now Playing: Trump sends National Guard to assist border 'crisis'

Now Playing: Senate Intel Republican: Trump 'frustrated' by investigation but won't fire Mueller

Now Playing: Top House Intel Democrat: Even if McCabe firing 'justified, it can also be tainted'

Now Playing: Chris Christie: 'I don't think it would be appropriate for' Trump to fire Mueller

Now Playing: Trump fires Tillerson, Sessions fires former FBI Deputy Director McCabe