Four of the gunshot victims are teenagers.
The suspect used the screen name "Adolf Hitler (((6 Million)))" while gaming online, according to reports.
Witnesses who attempted to leave the store told reporters that the emergency exits wouldn't open, leading to chaos.
"We stand right now on behalf of our president, and we pray for your grace and your mercy and your wisdom upon him," McLean Bible Church Lead Pastor David Platt said to his congregation as President Trump stood beside him on stage.
At around 8 p.m. on Saturday, police responded to a shooting at the Holiday Plaza shopping center in Stockton, California, where they found five victims suffering from gunshot wounds.
"She appeared to have died from a self-inflicted wound," Dean Phillips, special agent in charge of the Denver field office of the FBI, confirmed.
"I want to get rid of that fear," said Representative Eric Swalwell, who launched his campaign for the Democratic presidential nomination last week.
"I adore and support [Dylann Roof] and have since day one," one post on Tumblr read.
A handwritten letter and a note on a bathroom wall each threatened mass violence against the university.
"Remarkably, however, over the last ten years Mr. Choochongkol has primarily relied on his participation in human drug trials in order to support him and his wife."
"This is the new normal, if you look across the country," said Kern County sheriff Donny Youngblood.
Is the best we can hope for shootouts in classrooms?
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.
Our kids go to school to learn math and science, not how to duck and cover.
Since the Parkland, Florida, shooting, we've seen a surge of support for prevention of gun violence.
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.