WASHINGTON, DC - JULY 12: The presidential helicopter Marine One lands on the South Lawn of the White House before picking up U.S. President Barack Obama and first lady Michelle Obama July 12, 2016 in Washington, DC. The Obamas are traveling to Dallas to attend a public memorial service for the five Dallas police officers who were killed by a sniper last week during a Black Lives Matter demonstration. (Photo by Chip Somodevilla/Getty Images)