: DALLAS, TX – JULY 12: U.S. President Barack Obama and first lady Michelle Obama embrace former U.S. President George W. Bush during an interfaith memorial service, honoring five slain police officers, at the Morton H. Meyerson Symphony Center on July 12, 2016 in Dallas, Texas. A sniper opend fire following a Black Lives Matter march in Dallas killing five police officers and injuring 12 others. Tom Pennington/Getty Images/AFP == FOR NEWSPAPERS, INTERNET, TELCOS & TELEVISION USE ONLY ==

: US President Barack Obama pauses while speaking during an interfaith memorial service for the victims of the Dallas police shooting at the Morton H. Meyerson Symphony Center on July 12, 2016 in Dallas, Texas. President Barack Obama attended a somber memorial Tuesday to five police officers slain in a sniper ambush in Dallas, as he seeks to unify a country divided by race and politics. / AFP / MANDEL NGAN

: Photos of the victims of the Dallas police shooting are seen during an interfaith memorial service at the Morton H. Meyerson Symphony Center on July 12, 2016 in Dallas, Texas. President Barack Obama attended a somber memorial Tuesday to five police officers slain in a sniper ambush in Dallas, as he seeks to unify a country divided by race and politics. / AFP / MANDEL NGAN

: President Barack Obama, pauses while speaking during a memorial service at the Morton H. Meyerson Symphony Center, Tuesday, July 12, 2016, in Dallas, for five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. Seated, from left are, Jill Biden, Vice President Joe Biden, former first lady Laura Bush, former president George W. Bush, first lady Michelle Obama and Dallas Mayor Mike Rawlings. (AP Photo/Eric Gay)

: President Barack Obama, third form right, gives DART Police Chief J.D. Spiller a hug as first lady Michelle Obama hugs Dallas Police Chief David Brown, center, after an interfaith memorial service for five fallen officers at the Morton H. Meyerson Symphony Center in Dallas, Tuesday, July 12, 2016. Joining him were President George W. Bush and former first lady Laura Bush greeting Micki Rawlings, wife of Dallas Mayor Mike Rawlings. Four Dallas police officers and one DART officer were fatally shot last week in Dallas at a protest rally. (Tom Fox/The Dallas Morning News via AP)

: El presidente Barack Obama y la primera dama Michelle Obama asisten a una ceremonia interreligiosa para los agentes caídos y los miembros de la comunidad de Dallas en el Centro Sinfónico Morton H. Meyerson en Dallas, el martes 12 de julio de 2016. (AP Foto/Susan Walsh)