"This attack shocked the conscience of our nation and filled our hearts with grief," Trump said at the start of a White House tax event. "Journalists, like all Americans, should be free from the fear of being violently attacked while doing their job."
"We pledge our eternal support," he added. "My government will not rest until we have done everything in our power to reduce violent crime and to protect innocent life."
Trump did not address gun control, or the current climate of hostility journalists face.
The president's remarks are his first on-camera response to the shooting. Following the attack on Thursday, Trump expressed his condolences to the families of the victims and thanked first responders in a tweet. Press Secretary Sarah Sanders also issued a statement on Thursday after the shooting, calling the attack an "evil act of senseless violence."
Trump ignored shouted questions about the attack from reporters at the White House on Thursday.
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The shooting suspect's apparent motive was a personal vendetta he had with the newspaper for covering his arrest on harassment charges, though experts noted Thursday the increasing rancor journalists have confronted on the job.
Earlier this week, Trump, who often uses the term "fake news" to denounce journalists for coverage critical of him, called the press "the enemy of the people" at a South Carolina rally. He has used that phrase several times over the course of his presidency in speeches and on Twitter.
The shocking attack on an American newsroom stunned the country. Reporters at the paper described the incident in real time and prompted police forces across the country to send officers to news organizations as a precaution.
Phil Davis, a Gazette crime reporter who was in the office at the time of the shooting, recounted the experience on Twitter.
"Gunman shot through the glass door to the office and opened fire on multiple employees," Davis wrote in a post on Twitter. "Can't say much more and don't want to declare anyone dead, but it's bad."
“There is nothing more terrifying than hearing multiple people get shot while you’re under your desk and then hear the gunman reload,” Davis later tweeted.
Police described the shooting as a "targeted attack."
The suspect, Jarrod Ramos, 38, stormed into the newsroom Thursday afternoon with a shotgun and smoke grenades, officials said. Police were notified about an active shooter at the newspaper around 2:40 p.m. and arrived to the scene within 30 seconds, authorities said.
Officials said there was no exchange of gunfire between the gunman and police.
Ramos was charged Thursday with five counts of first-degree murder and appeared in court on Friday for a bail hearing.