The Orlando Police Department released this photo of Omar Mateen, the person identified as the shooter in the Orlando terror attack.
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Investigators look into the past of Omar Mateen
The Lead
Investigators are working to figure out why Omar Mateen carried out the deadliest mass shooting in U.S. history. CNN's Drew Griffin reports.
01:53 - Source: CNN
Orlando Nightclub Mass Shooting 32 videos
The Orlando Police Department released this photo of Omar Mateen, the person identified as the shooter in the Orlando terror attack.
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Investigators look into the past of Omar Mateen
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How Orlando shooting unfolded, as seen via texts
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WASHINGTON, DC - JUNE 14: (AFP-OUT) US President Barack Obama speaks on the Orlando shooting at the Treasury Department after convening with his National Security Council on June 14, 2016 in Washington, DC. Obama directly attacked Donald Trump's proposal to ban Muslims from entering the United States. (Photo by Jim Lo Scalzo-Pool/Getty Images)
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Key moments: Obama's 'radical Islam' pushback
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Orlando shooter's dad: I didn't notice anything
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The Orlando Police Department released this photo of Omar Mateen, the person identified as the shooter in the Orlando terror attack.
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Officials: FBI had investigated Orlando gunman
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Orlando Police officers direct family members away from a multiple shooting at a nightclub in Orlando, Fla., Sunday, June 12, 2016. A gunman opened fire at a nightclub in central Florida, and multiple people have been wounded, police said Sunday.
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Deadly Orlando shooting attack in 90 seconds
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Rubio on shooting: I fear 'we will see more of this'
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An image taken from Omar Mateen's Myspace page. Law enforcement sources identified Mateen as the shooter in the Orlando terror attack.
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Gunman called 911, claimed allegiance to ISIS
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Ex-wife of Orlando shooter speaks out
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A shooting and multiple injuries were reported at Pulse nightclub in Orlando.
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Eyewitness records video of police storming club
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Obama: This was an attack on all of us
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Witness: 'No bullet could ever break a friendship'
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Muslim leader to ISIS: 'You do not speak for us'
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Orlando Nightclub shooting pulse
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Mayor: 50 dead in Orlando nightclub shooting
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Pulse DJ recounts shooting inside Orlando nightclub
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Witness: 'Blood everywhere' after Orlando club shooting
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Victims in the Orlando shooting named
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How did the Orlando medical center respond?
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Orlando nightclub shootout caught on camera
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December 16, 2012 -- The shooting at Newton killed 20 children and six adults. At the memorial service, President Obama also cited the deadly shootings at Oak Creek and Aurora. "In the coming weeks, I will use whatever power this office holds to engage my fellow citizens -- from law enforcement to mental health professionals to parents and educators -- in an effort aimed at preventing more tragedies like this," said the president.
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Responding in the midst of tragedy
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Orlando police officers seen outside of Pulse nightclub.
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Witness: We thought gunshots were 'part of the music'
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Former Afghan Pres.: We condemn deadly Orlando attack
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A target sheet hangs at a shooting range July 22 in Aurora, Colorado.
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Orlando nightclub shooter identified
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Handguns that were swapped for gift cards during a Los Angeles Police Department sponsored gun buyback event in Los Angeles, California on December 13, 2014. The city held the event in three locations and the public were able safely and anonymously surrender firearms in exchange for $100 and $200 gift cards. AFP PHOTO/MARK RALSTON (Photo credit should read MARK RALSTON/AFP/Getty Images)
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Survivors of gun violence are fed up
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Police: Approx. 20 dead in Orlando nightclub shooting
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A shooting and multiple injuries were reported at Pulse nightclub in Orlando.
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Police: Shooter inside the nightclub is dead
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Police: 'Mass casualty situation' at Orlando nightclub
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Several injured in Florida nightclub shooting
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