Rumours about politically motivated vandals targeting gravestones at the site of the pivotal battle in the US Civil War appear to have started on a hoax Facebook page.
Saturday marks the 154th anniversary of one of the turning points in American history - the start of the Battle of Gettysburg. Over three days, Union troops held off Confederate soldiers, paving the way for the eventual victory of the north over the south and the reunification of the United States.
A slate of events will be held at the site of the battle over the weekend. But the political atmosphere in America has given rise to fake rumours about the potential for vandalism and violence at the site. Among the rumours is a report that far-left "antifa" (short for "anti-fascist") activists are planning to destroy Confederate gravestones.
The rumours initially seem credible, but there's a problem: although there is a cemetery at Gettysburg, no Confederate graves at the site are marked by stones.
Gettysburg commemorations have previously prompted rallies by free speech and pro-Confederate protesters, along with counter-protests by their opponents. In March 2016, for instance, a few hundred protesters and counter-protesters gathered at the site. Police kept both sides apart.
This year, multiple blogs and conservative websites indicated that protesters were planning to burn Confederate flags or desecrate Confederate graves. While Gettysburg National Military Park officials are prepared for protests, rally organisers say violence is not expected.
The Confederate flag has long been controversial. Its supporters say it's a symbol of the region which represents freedom and liberty, while its opponents point out that the Confederacy was built on the slave labour of African-Americans, an issue that was at the heart of the US Civil War.
At the same time, clashes involving far-right and far-left protesters have become more common on American streets.
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So why the confusion?
Inserted into this story have been online troublemakers intent on fooling their political opponents. Earlier this year, a Facebook event created by a group called "Trolling Trumpsters" suggested that people "desecrate Confederate Cemeteries" on Confederate Memorial Day in May. It was widely shared online.
The event suggested that protesters target the Marietta Confederate Cemetery, which contains more than 3,000 graves of Confederate soldiers.
The event prompted outrage - but no actual vandalism. Supporters of the Confederate flag turned up at the cemetery on 13 May. Local reports indicated that the group included "heavily armed" and alleged members of the Ku Klux Klan, but no one from the "Trolling Trumpsters" group appeared, and cemetery staff said they didn't notice any damage to graves.
The "Trolling Trumpsters" group has since been deleted from Facebook but by looking at archived copies of the site, it is possible to see that it was focused on creating anti-Trump memes and making events which would bait and upset conservatives.
For instance, they also planned a second event which almost 1,000 people said they would attend at Gettysburg, where they have threatened to burn a Confederate flag. People who tried to buy "tickets" for the event were directed to the donations page for the Southern Poverty Law Centre.
Several blogs documented their attempts to use Facebook's reporting systems to shut down the group, while others pointed to it as an example of how militant political activists are trying to undermine Donald Trump's presidency.
There will be some protests at Gettysburg this year - special permits have been granted not to antifa activists but to three conservative groups. Two of the groups are explicit Confederate flag supporters, but the third group, "Support America and her history" appears to be reacting to the flag-burning event, and have encouraged people to rally in support of military veterans.
With reporting by Mike Wendling