A Dallas Area Rapid Transit police officer receives comfort at the Baylor University Hospital emergency room entrance on Thursday night.

A clerk looks at broken windows that were shot out at a store in downtown Dallas.

A Dallas police officer, who did not want to be identified, takes a moment as she guards an intersection early Friday morning.

Reunion tower, right, stands with the lights out as the sun rises over downtown Dallas on Friday. Many Dallas business turned out their lights to honor the police killed and wounded in an attack Thursday evening.

A crime scene investigator looks a shot out windows in downtown Dallas on Friday.

Police take cover after shots were fired during the Dallas protest.

Police move to detain a driver after the sniper attacks in Dallas.

Dallas Police respond after shots were fired at a Black Lives Matter rally in downtown Dallas on Thursday.

A Dallas police officer covers his face as he stands with others outside the emergency room at Baylor University Medical Center.

Dallas police respond after shots were fired at a protest in downtown Dallas on Thursday night over the killing of Alton Sterling by police officers in Baton Rouge, La., and Philando Castile, who was killed by police less than 48 hours later in Minnesota.

A police officer keeps watch on a street in downtown Dallas after shots were fired during a protest over two fatal police shootings of black men.

Police respond after shots were fired Thursday night in downtown Dallas. Three officers died and three others were critically injured.

Police move to detain a driver after snipers shot 11 police officers in downtown Dallas.

An officer moves to detain a driver after 11 police officers were shot in downtown Dallas on Thursday night. Snipers apparently shot the officers, the city's chief said.

An officer stands watch after the shooting in downtown Dallas.

Police and others gather at the emergency entrance to Baylor Medical Center in Dallas, where several police officers were taken after the shootings.

Dallas police on the scene after the fatal shootings.

Dallas police chief David Brown, front, and Dallas mayor Mike Rawlings, rear, talk with the media during a news conference on Friday.

Dallas police officers stand in a line near the site of shootings in downtown Dallas, early Friday morning.

Dallas police chief David Brown, left, and Dallas mayor Mike Rawlings, right, talk with the media during a news conference on Friday.

Investigators walk the scene of a shootings in downtown Dallas.

Dallas Mayor Mike Rawlings, right, talks with unknown persons as he arrives at the emergency room at Baylor University Medical Center Friday morning.