One woman was killed and another 13 people wounded in Sunday night's attack.
The teens had created a hit list, researched bomb-making techniques and were hoarding weapons before their arrest.
James Shaw Jr., 29, reportedly disarmed the gunman who used an assault rifle to kill four people at a Tennessee Waffle House on Sunday.
In an address to the country on Thursday morning, the president discussed tackling "the difficult issue of mental health," but did not mention gun control.
The FBI was alerted to Nikolas Cruz after someone with the same username posted a comment on YouTube last fall proclaiming, "I'm going to be a professional school shooter."
The documents also identified a second person of interest in the case.
Lawyers for police argued authorities could not release sealed documents because they are investigating more charges.
“Now that’s a long time for some people, but speaking for the FBI, that’s light speed," the agent told a Nevada newspaper.
Aztec High School shooter who killed two joked about Columbine online and went by the usernames “Adam Lanza” and “Future Mass Shooter,” among others.
"It will be great, right?" the suspect allegedly said.
“What kind of security tops God’s protection?” a religion professor asked.
Some attorneys say MGM's paid room for its security guard could result in him providing a version of the shooting timeline that is favorable to the company.
Alan Ashmore, 61, is alleged to have killed two and injured two others—including a police officer.
“Scariest moment of my life,” one Instagram user wrote, posting video of the terrified crowd. “They just kept firing and firing.”
There have been 244 mass shootings in the U.S. in 2017 thus far.
If the NRA's claim that guns help reduce crime were true, the U.S. would have the lowest homicide rate among industrialized nations instead of the highest one.
Just a few hours after the Virginia shooting, another mass shooting took place in California.
The victims were killed in four locations, some while in their beds.
Jason Dalton, the Uber driver suspected in this past weekend’s deadly shooting spree in Kalamazoo, Michigan, may have switched cars before the lethal rampage.
Jason Dalton, 45, faces 16 charges, including six of murder, which can bring up to life in prison.