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People run for cover at the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada.  (Photo by David Becker/Getty Images)

 
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A person takes cover at the Route 91 Harvest country music festival after apparent gun fire was heard on October 1, 2017 in Las Vegas, Nevada. (Photo by David Becker/Getty Images)

 
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A police helicoper circles the Mandalay Bay and Luxor hotels on October 1, 2017 in Las Vegas, Nevada. A gunman opened fire on a music festival in Las Vegas, killing at least 20 people. (Photo by David Becker/Getty Images)

 
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Las Vegas Metropolitan Police officers run down Tropicana Ave. near Las Vegas Boulevard after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

 
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An injured person is tended to in the intersection of Tropicana Ave. and Las Vegas Boulevard after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

 
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People tend to the wounded outside the Route 91 Harvest Country music festival grounds after an apparent shooting on October 1, 2017 in Las Vegas, Nevada. (Photo by David Becker/Getty Images)

 
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People run from the Route 91 Harvest country music festival after apparent gun fire was hear on October 1, 2017 in Las Vegas, Nevada.(Photo by David Becker/Getty Images)

 
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People run from the Route 91 Harvest country music festival after gun fire was heard on October 1, 2017 in Las Vegas, Nevada. (Photo by David Becker/Getty Images)

 
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An ambulance leaves the intersection of Las Vegas Boulevard and Tropicana Ave. after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

 
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A man lays on top of a woman as others flee the Route 91 Harvest country music festival grounds after a active shooter was reported on October 1, 2017 in Las Vegas, Nevada.  (Photo by David Becker/Getty Images)

 
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A Las Vegas Metropolitan Police officer stands in the intersection of Las Vegas Boulevard and Tropicana Ave. after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

 
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Police officers stand by as medical personnel tend to a person on Tropicana Ave. near Las Vegas Boulevard after a mass shooting at a country music festival nearby on October 2, 2017 in Las Vegas, Nevada . (Photo by Ethan Miller/Getty Images)