As many as 600 New Year's Eve revelers were inside the Reina nightclub when a gunman entered and started firing. Turkish officials said at least 39 people were killed and nearly 70 were injured.
Istanbul Nightclub New Year's Eve Terror Attack

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Ambulances wait near the scene of an attack in Istanbul, early Jan. 1, 2017.

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Police forensic experts examine an area near an Istanbul nightclub, following a gun attack, Jan. 1, 2017.

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Young people leave the scene of an attack in Istanbul, early Jan. 1, 2017. An assailant opened fire at a nightclub in Istanbul's Ortakoy district during New Year's celebrations, killing dozens of people and wounding dozens more.

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Youths embrace near the scene of an attack in Istanbul, early Jan. 1, 2017. An assailant believed to have been dressed in a Santa Claus costume and armed with a long-barreled weapon, opened fire at a nightclub in Istanbul's Ortakoy district.