Journalists around the nation are reeling after a lone gunman attacked a Maryland newsroom on Thursday, making it the deadliest day for the profession since Sept. 11, 2001.

A suspect is in custody following the shooting at the Capital Gazette office in Annapolis. A reporter who was in the newsroom at the time said the gunman shot through a glass door before opening fire on the reporters colleagues, killing at least five people and injuring several more. Police have not yet given a concrete motive, but the massacre already serves as a grim marker for the field of journalism.

Prior to Thursdays attack, at least 32 journalists and media staff had been killed in the U.S. since 1990, according to the International Federation of Journalists . Eight died on 9/11, though only photojournalist Bill Biggart, who was struck by falling debris while taking pictures of the World Trade Centers collapse, was killed while covering the events of that day. Six TV engineers were among those who perished inside the World Trade Center. Another professional photojournalist was aboard one of the hijacked planes.

The tally of slain journalists varies slightly depending on methodology. The Committee to Protect Journalists counts Biggart as the lone journalist death on 9/11. According to CPJ, the previous deadliest day for journalists in the past quarter-century came in 2015, when WDBJ-TV reporter Alison Parker and cameraman Adam Ward were killed by a former co-worker during an on-air interview.

But Thursdays massacre appears to be the first mass shooting involving journalists in the U.S. and one of the deadliest targeted attacks on the American press. A bombing at the Los Angeles Times building in 1910 killed 21 people, though it wasnt clear that the pro-union perpetrators intended to kill reporters.

Although we dont yet know if the gunman in Annapolis chose to target the Capital Gazette newsroom out of a broader animosity for the media, the killings come at a time of escalating antagonism toward the press, often at the urging of those in the highest ranks of power.

Weve seen a lot of threats against journalists over the past two years. Weve seen a lot of chilling statements from politicians, especially [President] Donald Trump, demonizing the press, said Peter Sterne, a senior reporter for Freedom of the Press Foundation and managing editor of the U.S. Press Freedom Tracker , a project that has been documenting hostility against journalists in the past few years.

Trump has regularly maligned the media, accusing news outlets of deliberately lying about his administration to make him look bad. Hes also referred to the press as the enemy of the people, echoing a phrase used by some of historys most notorious dictators, as well as by former President Richard Nixon.

That sort of language has become common fare for Trump and many of his supporters. And as any reporter whos been online in the past three years can attest, its not unusual for the criticism to boil over into more violent threats.

But the attacks on the media havent only been rhetorical. There have also been plenty of assaults on individual journalists, said Sterne, often involving protesters of various ideological bents shoving or punching reporters, or stealing cameras.

Last year, Republican candidate Greg Gianforte body-slammed a reporter on the eve of the Montana special election that sent him to Congress. Gianforte later pleaded guilty to assault and avoided jail time.

To Sterne, the onslaught of verbal and physical jabs has contributed to an atmosphere that has many journalists fearing for their safety.

I do think there is a tie between some of the rhetoric that people use to demonize journalists and the increasing number of attacks on journalists, said Sterne. Theres definitely a sense that when people are unhappy with journalists coverage, they increasingly are resorting to physical means.

As the attack on the Capital Gazette shows, these threats can be deadly serious.

CORRECTION: An earlier version of this article said that Alison Parker and Adam Ward were with WXAN. They worked for WDBJ-TV.