ANNAPOLIS (Maryland) • In the shade of a carpark in Maryland's capital Annapolis, three journalists from the Capital Gazette typed grimly away, still without news of colleagues killed or injured when a gunman stormed the publication.

"We're putting out a paper tomorrow," vowed Mr Chase Cook, one of six reporters at the daily, where the latest mass shooting to rock the United States left five people dead on Thursday.

His photographer colleague Joshua McKerrow had his laptop perched on the back of a pickup truck. Their deadline had been pushed back to 9.30pm. Mr Chase was working from his smartphone - from which he could access the newspaper's editorial system.

"We're going to have a paper," said the young man, who has worked since 2013 for The Capital, a local daily whose roots go back to 1727 - and which police believe was deliberately targeted in Thursday's attack. "I don't know what else to do except this," he said. "We're just doing our job."

He was not inside the paper's offices when the gunman burst in and opened fire. "All I know is five people are dead," he said.

Past and present employees of the newspaper chain were struggling to understand what could have prompted such an attack.

"The Capital, like all newspapers, angered people every day in its pursuit of the news," Mr Tom Marquardt, a former executive editor and publisher at The Capital, wrote on Facebook.

"In my day, people protested by writing letters to the editor; today it's through the barrel of a gun. Sure, I had death threats and the paper had bomb threats. But we shrugged them off as part of the business we were in."

Mr Jimmy DeButts, an editor at the Capital Gazette, tweeted that he was devastated, heartbroken and numb. "I'm in no position to speak, just know @capgaznews reporters & editors give all they have every day. There are no 40-hour weeks, no big paydays - just a passion for telling stories from our community," he wrote.

Yesterday, The Capital newspaper, part of the Gazette group, published an edition with photographs of each of the victims along with "5 shot dead at The Capital" as a headline in large bold lettering on its front page.

Police were looking into social media threats received by the paper, which employs a small team out of a ground-floor office. It took officers - trained to respond to the mass shootings that have become a regular occurrence in the country - just 60 seconds to arrive on site, according to an official.

Mr Sean Robinson, who works for an insurance company on the building's top floor, took shelter as far away as possible from the entrance and texted his wife to say, "Hey, this is going on. Just pray."

Two floors down, Ms Gracie Rustin, a young dental assistant, heard several sets of "loud noises", but didn't immediately realise it was a shooting. From a nearby shopping centre, where she was escorted to safety along with other office workers, she recounted how the police rushed in and evacuated everyone: "They were like, 'Leave, leave, leave!' "

"As soon as the elevator doors opened, the cops with guns were like, 'Hands up! Hands up!' and I just started crying immediately."