Major Incidents | Slideshow

Sniper Kills Dallas Police Officers

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Sniper Kills Dallas Police Officers

Police and others gather at the emergency entrance to Baylor Medical Center in Dallas, where several police officers were taken after shootings Thursday, July 7, 2016.. (AP Photo/Emily Schmall)

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Sniper Kills Dallas Police Officers

Dallas police crime scene investigators record evidence surrounding a police cruiser parked at the emergency room at Baylor University Medical Center, Friday, July 8, 2016, in Dallas. Snipers opened fire on police officers in the heart of Dallas on Thursday night, killing some of the officers. (AP Photo/Tony Gutierrez)

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Sniper Kills Dallas Police Officers

A Dallas police officer, who did not want to be identified, takes a moment as she guards an intersection in the early morning after a shooting in downtown Dallas, Friday, July 8, 2016. At least two snipers opened fire on police officers during protests in Dallas on Thursday night; some of the officers were killed, police said. (AP Photo/LM Otero)

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Sniper Kills Dallas Police Officers

A Dallas police officer steps out of a vehicle as he arrives in front of Baylor University Medical Center where several others were police were already gathered, Friday, July 8, 2016, in Dallas. At least two snipers opened fire on police officers in Dallas on Thursday night, police said. (AP Photo/Tony Gutierrez)

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Sniper Kills Dallas Police Officers

A Dallas police vehicle follows behind an ambulance carrying a patient to the emergency department at Baylor University Medical Center, as police and others stand near the emergency entrance early Friday, July 8, 2016, in Dallas. At least two snipers opened fire on police officers in Dallas on Thursday night during protests over two recent fatal police shootings of black men, police said. (AP Photo/Tony Gutierrez)

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Sniper Kills Dallas Police Officers

A Dallas police officer covers his face as he stands with others outside the emergency room at Baylor University Medical Center, Friday, July 8, 2016, in Dallas. Snipers opened fire on police officers in the heart of Dallas on Thursday night, killing some of the officers. (AP Photo/Tony Gutierrez)

07 / 14

Police Shootings Protests Dallas

Dallas police respond after shots were fired during a protest over recent fatal shootings by police in Louisiana and Minnesota, Thursday, July 7, 2016, in Dallas. Snipers opened fire on police officers during protests; several officers were killed, police said. (Maria R. Olivas/The Dallas Morning News via AP)

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Police Shootings Protests Dallas

Dallas police respond after shots were fired during a protest over recent fatal shootings by police in Louisiana and Minnesota, Thursday, July 7, 2016, in Dallas. Snipers opened fire on police officers during protests; several officers were killed, police said. (Maria R. Olivas/The Dallas Morning News via AP)

09 / 14

Police Shootings Protests Dallas

Dallas police respond after shots were fired during a protest over recent fatal shootings by police in Louisiana and Minnesota, Thursday, July 7, 2016, in Dallas. Snipers opened fire on police officers during protests; several officers were killed, police said. (Maria R. Olivas/The Dallas Morning News via AP)

10 / 14

Police Shootings Protests Dallas

Dallas police respond after shots were fired during a protest over recent fatal shootings by police in Louisiana and Minnesota, Thursday, July 7, 2016, in Dallas. Snipers opened fire on police officers during protests; several officers were killed, police said. (Maria R. Olivas/The Dallas Morning News via AP)

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Sniper Kills Dallas Police Officers

The El Centro College parking garage stands in downtown Dallas early Friday, July 8, 2016. Snipers opened fire on police officers in Dallas, killing several during protests over two recent fatal police shootings of black men, police said. Police said three suspects were in custory and a fourth suspect was exchanging gunfire with authorities, Dallas Police Chief David Brown said early Friday morning. The suspect is not cooperating and has told negotiators he intends to hurt more law enforcement officials, the chief said. (AP Photo/LM Otero)

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Sniper Kills Dallas Police Officers

Dallas police move to detain a driver after several police officers were shot in downtown Dallas, Thursday, July 7, 2016. At least two snipers opened fire on police officers during protests in Dallas on Thursday night; some of the officers were killed, police said. (AP Photo/LM Otero)

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Sniper Kills Dallas Police Officers

Dallas police move to detain a driver after several police officers were shot in downtown Dallas, Thursday, July 7, 2016. At least two snipers opened fire on police officers during protests Thursday night; some of the officers were killed, police said. (AP Photo/LM Otero)

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Sniper Kills Dallas Police Officers

Law enforcement sweep the area after a shooting in downtown Dallas, Friday, July 8, 2016. At least two snipers opened fire on police officers during protests in Dallas on Thursday night; some of the officers were killed, police said. (AP Photo/LM Otero)