Attacker Connor Betts, 24, was killed by police within 30 seconds of the first shots being fired outside a bar in the city's entertainment district.
Senate majority leader trends on Twitter for the second time in a week following mass shootings in Texas and Ohio.
Christian Picciolini, who founded an anti-extremist group, suggested that domestic white supremacist attacks are part of a "transnational terror network."
"The ultimate amplifier on this kind of hate is the bully pulpit of the White House," the 2020 Democratic presidential candidate said.
At least two high-level Republican lawmakers blamed video game violence for "dehumanizing" people and encouraging the El Paso, Texas and Dayton, Ohio mass shootings over the past 24 hours.
The El Paso Police Department initially tweeted that there were reports of "multiple shooters" but only had one person in custody.
"Read Might Is Right by Ragnar Redbeard," gunman Santino William Legan wrote in an Instagram post before shooting.
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.