President Barack Obama hugs Dallas Police Chief David Brown during a memorial service at the Morton H. Meyerson Symphony Center in Dallas on Tuesday. Senate Majority Whip John Cornyn of Texas and Dallas Mayor Mike Rawlings, applaud.

A woman wipes away tears during a memorial service at the Morton H. Meyerson Symphony Center for fallen police officers on Tuesday in Dallas.

An honor guard marches past the portraits of the five fallen officers as a memorial service gets underway at the Morton H. Meyerson Symphony Center in Dallas on Tuesday.

President Barack Obama holds hands with Dallas Mayor Mike Rawlings and first lady Michelle Obama during an interfaith memorial service for the fallen police officers and members of the Dallas community at the Morton H. Meyerson Symphony Center in Dallas on Tuesday.

President Barack Obama and former President George W. Bush shake hands as first lady Michelle Obama, and Laura Bush, left, stand by after Bush spoke during a memorial service at the Morton H. Meyerson Symphony Center in Dallas on Tuesday.

A singer performs during an interfaith memorial service for the fallen police officers and members of the Dallas community on Tuesday at the Morton H. Meyerson Symphony Center in Dallas. 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 and President Barack Obama.

Law enforcement officers attend an interfaith memorial service for the fallen police officers and members of the Dallas community on Tuesday at the Morton H. Meyerson Symphony Center in Dallas.

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 at the Morton H. Meyerson Symphony Center in Dallas on Tuesday.

A group of McKinney police officers arrives for an interfaith memorial service at the Morton H. Meyerson Symphony Center in Dallas on Tuesday for five law enforcement officers killed last week while standing guard as hundreds of people peacefully protested the police killings of black men in Louisiana and Minnesota earlier in the week.

Seats are left empty in honor of five fallen law enforcement officers are at an interfaith memorial service at the Morton H. Meyerson Symphony Center in Dallas on Tuesday.

Dallas Area Rapid Transit police officer Misty McBride, right, is embraced by a fellow officer as she arrives for a memorial at the Morton H. Meyerson Symphony Center on Tuesday in Dallas. Five police officers were killed and several injured, including McBride, during a shooting in downtown Dallas last Thursday night.

Officials stand for the national anthem during a memorial service at the Morton H. Meyerson Symphony Center with the families of the fallen police officers on Tuesday in Dallas.

A member of the Dallas Police Choir passes the portraits of five fallen officers prior to a memorial service at the Morton H. Meyerson Symphony Center on Tuesday in Dallas.

President Barack Obama and first lady Michelle Obama attend an interfaith memorial service for the fallen police officers and members of the Dallas community at the Morton H. Meyerson Symphony Center in Dallas on Tuesday.

Joseph Scott holds a sign outside the memorial for fallen Dallas officers in downtown Dallas on Tuesday.

Law enforcement officers stand guard outside the memorial for fallen Dallas officers in downtown Dallas on Tuesday.

A flag flies outside the memorial for fallen officers in downtown Dallas on Tuesday.

President Barack Obama heads to Air Force One at Andrews Air Force Base in Md., on Tuesday, as he traveled to Dallas to speak at an interfaith memorial service for the fallen police officers and members of the Dallas community.