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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 PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

Police Officers escort the body of Sergeant Michael Smith into Mary Immaculate Catholic Church in Farmers Branch, Texas, on July 12, 2016. Sargent Smith was killed in the recent sniper attack at a protest in Downtown Dallas. / AFP PHOTO / Laura Buckman/AFP / Laura BuckmanLAURA BUCKMAN/AFP/Getty Images

Dallas Police Chief David Brown speaks 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 PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

DALLAS, TX - JULY 12: U.S. President Barack Obama delivers remarks 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. (Photo by Tom Pennington/Getty Images)

President Barack Obama hugs Dallas Police Chief David Brown during a memorial service at the Morton H. Meyerson Symphony Center in Dallas, Tuesday, July 12, 2016. Senate Majority Whip John Cornyn of Texas, and Dallas Mayor Mike Rawlings, applaud. Five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. (AP Photo/Eric Gay)

President Barack Obama, left, and first lady Michelle Obama, center, reach out to former President George W. Bush, left during a memorial service at the Morton H. Meyerson Symphony Center with the families of the fallen police officers, Tuesday, July 12, 2016, in Dallas. Five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. (AP Photo/Eric Gay)

DALLAS, TX - JULY 12: Officials, including U.S. President Barack Obama, first lady Michelle Obama, former U.S. President George W. Bush, former first lady Laura Bush and Dallas Police Chief David O. Brown, join in singing the 'Battle Hym of the Republic' 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. (Photo by Tom Pennington/Getty Images)

Portraits of the five fallen police officers are seen at rear as a memorial gets underway at the Morton H. Meyerson Symphony Center in Dallas, Tuesday, July 12, 2016, after the arrival of President Barack Obama. Five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. (AP Photo/Eric Gay)

Former US president George W. Bush speaks 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 embarked on a somber visit to Dallas Tuesday, to memorialize five white police officers murdered by a black gunman and try to unify a country divided by race and politics. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

From left, Jill Biden, Vice President Joe Biden, former first lady Laura Bush, former President George W. Bush, Michelle Obama and President Barak Obama stand for the national anthem during an interfaith memorial service at the Morton H. Meyerson Symphony Center in Dallas on Tuesday, July 12, 2016, for five law enforcement officers killed last week in an ambush at a Black Lives Matter rally. (Smiley N. Pool/The Dallas Morning News via AP) /The Dallas Morning News via AP) MANDATORY CREDIT; MAGS OUT; TV OUT; INTERNET USE BY AP MEMBERS ONLY; NO SALES

Dallas Police Chief David Brown, at podium, speaks as President Barack Obama, former president George W. Bush and Vice President Joe Biden along with others stand and applaud during a memorial service at the Morton H. Meyerson Symphony Center, Tuesday, July 12, 2016, in Dallas. Five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. (AP Photo/Eric Gay)

First Lady Michelle Obama hugs Dallas Police Chief David Brown (2nd L) as US President Barack Obama hugs Dallas Area Rapid Transit Police Chief James Spiller (R) 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 PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

First lady Michelle Obama and President George W. Bush, flanked by President Barack Obama and former first lady Laura Bush, share a moment during a memorial service for five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night, Tuesday, July 12, 2016, at the Morton H. Meyerson Symphony Center in Dallas. (AP Photo/Eric Gay)

Law enforcement officers attend an interfaith memorial service for the fallen police officers and members of the Dallas community, Tuesday, July 12, 2016, at the Morton H. Meyerson Symphony Center in Dallas. (AP Photo/Susan Walsh)

President Barack Obama and former President George W. Bush bows their heads during an interfaith memorial service for the fallen police officers and members of the Dallas community, Tuesday, July 12, 2016, at the Morton H. Meyerson Symphony Center in Dallas. First lady Michelle Obama is at center. (AP Photo/Susan Walsh)

DALLAS, TX - JULY 12: DART officer Misty McBride (R) arrives at an interfaith memorial service, honoring five slain police officers, at the Morton H. Meyerson Symphony Center on July 12, 2016 in Dallas, Texas. McBride was injured when sniper opend fire following a Black Lives Matter march in Dallas killing five police officers and injuring 12 others. (Photo by Tom Pennington/Getty Images)

Former US president George W. Bush and former first lady Laura Bush attend 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. / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images

From left, Dallas Mayor Mike Rawlings, his wife Micki, Dallas Police Chief David Brown, Dallas Area Rapid Transit Police Chief, J.D. Spiller and Fort Worth, Texas Mayor Betsy Price, react to comments by President Barack Obama during a memorial service at the Morton H. Meyerson Symphony Center in Dallas, Tuesday, July 12, 2016. Five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. (AP Photo/Eric Gay)

From left, Vice President Joe Biden, former first lady Laura Bush, former President George W. Bush, first lady Michelle Obama, and President Barack Obama join hands during a memorial service at the Morton H. Meyerson Symphony Center with the families of the fallen police officers, Tuesday, July 12, 2016, in Dallas. Five police officers were killed and several injured during a shooting in downtown Dallas last Thursday night. (AP Photo/Eric Gay)

President Barack Obama pauses as he is applauded while speaking during an interfaith memorial service for the fallen police officers and members of the Dallas community, Tuesday, July 12, 2016, at the Morton H. Meyerson Symphony Center in Dallas. In the front row, from left are, Jill Biden, Vice President Joe Biden, former first lady Laura Bush, former President George W. Bush, and first lady Michelle Obama. (AP Photo/Susan Walsh)

From left, former first lady Laura Bush former President George W. Bush, first lady Michelle Obama, and President Barack Obama attend an interfaith memorial service for the fallen police officers and members of the Dallas community, Tuesday, July 12, 2016, at the Morton H. Meyerson Symphony Center in Dallas. (AP Photo/Susan Walsh)