Thursday's attack at the Capital Gazette newspaper is the deadliest day for journalism in America since 9/11.
Four people died at the newspaper's office in Annapolis, and a fifth person died after being transported to the hospital.
The identities of the victims were released on Thursday night. Rob Hiaasen, Gerald Fischman, Wendi Winters, and John McNamara were editors, and Rebecca Smith was an ad sales assistant for the paper.
"What happened here was very calculated," Capital Gazette reporter Selene San Felice said on "Anderson Cooper 360."
She was in the newsroom when the shots rang out. "I think this person was going after editors," she said.
Reporter Phil Davis said on "AC360" that he hid under a desk during the attack. When he heard the gunman reload, he said he wondered to himself, "Are we all going to die?"
Local authorities said the newspaper as a whole was "targeted." Multiple law enforcement officials have told CNN the suspect in the shooting is Jarrod Warren Ramos, who had previously filed a defamation lawsuit against the paper. The suit was dismissed.
News of the shooting spree caused a chill in newsrooms across the United States on Thursday. Law enforcement in several cities stepped up security around major news organizations as a precautionary measure.
Threats against members of the media have been on the rise in recent years. But murders of American journalists are very rare.
The last time multiple journalists were killed while on assignment in the U.S. was in 2015, when an ex-employee attacked two members of a WDBJ TV news crew during a live report in Virginia.
Reporter Alison Parker and photojournalist Adam Ward were killed. On Thursday, Chris Hurst, who was engaged to Parker when she was killed, tweeted in response to the Annapolis shooting, "The threat to journalists is real and became deadly once more today in Annapolis. My condolences to everyone impacted at the @capgaznews newsroom."
The Committee to Protect Journalists, which tracks threats to journalists around the world, said that "seven journalists have been killed in relation to their work in the United States" since the group began its tracking effort in 1992.
The group noted that "a music journalist was killed in Chicago" earlier this year, but "CPJ is still investigating the motive for that killing."
"Newspapers like the Gazette do vital work, and our thoughts are with them amid this unconscionable tragedy," the group's executive director Joel Simon said in a statement. "Violence against journalists is unacceptable, and we welcome the thorough investigation into the motivations behind the shooting."
CPJ's database includes one journalist death on 9/11 -- a freelance news photographer. Six broadcast engineers working for TV stations were also killed in the terror attacks, for a total of seven members of the news media.
That's why Thursday's death toll of five stands as the deadliest day for the industry since the terror attacks.
Capital Gazette Communications publishes multiple papers, including the Capital and the Maryland Gazette. Danielle Ohl, a reporter for The Capital, pointed out on Twitter that the shared newsroom has "about 20 news staffers, a few more advertising."
Despite the attack, The Capital will still be publishing a newspaper Thursday night. Multiple newsroom staffers, plus reporters from its parent company, The Baltimore Sun, are working on stories for Friday's edition.
The Sun is owned by Tronc, which operates papers in many local markets. Tronc executives are on the way to Annapolis, according to an internal memo from CEO Justin Dearborn Thursday night.
In the memo, obtained by CNN, Dearborn said that "out of abundant precaution, we are increasing security presence at the company."
He also reminded employees that counseling and support services are available. The company's papers in Maryland will have counselors on site in the coming days.
"We are focused on providing support to our colleagues and their families," Dearborn wrote in the memo. "Members of our corporate leadership team are traveling to Maryland immediately to assist our local leadership and employees in Annapolis and Baltimore."