In the weeks before Jan. 6, several members of a far-right militia group discussed the possibility of violence breaking out around the certification of President Joe Biden's election victory, an FBI agent testified on Thursday.
Under questioning by federal prosecutors, FBI special agent and witness Kelsey Harris read through a series of messages between Oath Keepers founder Stewart Rhodes and other members who were in Washington on Jan. 6, 2021, amid then-President Donald Trump's push to reverse his loss to Biden.
"Trump needs to know we support him in using the Insurrection Act ... and we will support him with our boots on the ground nationwide," Rhodes wrote in a December 2020 group chat with other Oath Keeper members, according to a copy of the message that Harris read and which was displayed for the jury.
"The only chance we/he has is if we scare the s--- out of them and convince them it will be torches and pitchforks if they don't do the right thing," Rhodes wrote, according to the message shown Thursday.
MORE: Oath Keepers trial: Defendants 'concocted plan for armed rebellion' on Jan. 6, prosecution saysAt the time, Trump was urging lawmakers not to certify Biden's win -- and he was urging his supporters to pressure Congress as lawmakers were gathering in the U.S. Capitol on Jan. 6.
Rhodes and four other Oath Keepers are on trial for seditious conspiracy. They have pleaded not guilty and their attorneys have argued they planned only to "do security" and are being politically persecuted for their pro-Trump beliefs.
The evidence prosecutors presented Thursday, via the messages that Harris read, was intended to bolster the government's case that Rhodes and the others "concocted a plan for an armed rebellion to shatter a bedrock of American democracy."
At one point, according to Thursday's testimony, Rhodes suggested to others that he believed the Oath Keepers would have the support of the Secret Service if Trump did invoke the Insurrection Act to try and block the transfer of power. But Rhodes added that the group would need to wait for Trump's call.
"I think the Secret Service would be happy to have us out there based on prior positive relations with him at a dozen Trump rallies," his message read, according to what was shown in court.
The messages presented also included exchanges with Rhodes and Oath Keeper defendant Kelly Meggs with one stating, "there is going to be blood in the streets no matter what."
According to what was presented Thursday, Meggs also sent a picture of a tree with words superimposed reading, "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants."
In the messages displayed by the prosecution, which the defense attorneys have maintained are being mischaracterized, the Oath Keeper members went back and forth discussing whether Trump would back their efforts. Meggs at one point appeared to reference a statement from Trump in which he said Jan. 6 was going to be "wild."
MORE: Ex-Oath Keeper says 'many weapons' were stored outside capital during Jan. 6 attack"He called us all to the Capitol and wants us to make it wild," Meggs wrote. "Sir yes sir!!"
Rhodes is not accused of entering the Capitol during the insurrection and his attorneys insist he didn't direct anyone to do so, but prosecutors have contended he was a ringleader.
Three of the other four defendants in the ongoing trial did enter the Capitol: Kenneth Harrelson, Meggs and Jessica Watkins. The fourth, Thomas Caldwell, did not.
A former member of the Oath Keepers testified Wednesday about a large stash of weapons stored by the group at a hotel just outside Washington on Jan. 6 in what was intended to be a "quick reaction force."
The former member, Terry Cummings, testified that he had brought his own assault-style firearm as a "show of force" to deter potential attacks. Cummings has not been charged or accused of wrongdoing in connection with Jan. 6.
On Thursday, the jury was shown a video that appeared to be a promotional ad for the Oath Keepers in which members were seen holding weapons and wearing military-style uniforms as seeming examples of their law-enforcement style training.
FBI agent Harris testified to a picture of a guillotine posted on social media that was made to look like a hardware store ad along with this text: "Something you can do with your $600 stimulus check."
Meggs, one of the defendants, commented on that post: "We need to get these politicians and let them know who runs this country."
Rhodes attorney Phillip Linder said last week, in an opening statement, that prosecutors were cherry-picking past statements.
"You take a handful of texts and you take a handful of things you don't understand, take some things that look bad and put them together then you come to a conclusion or an incorrect mischaracterization," Linder said then. "We want to bring you the full picture."
Under cross-examination on Thursday by one of Rhodes' defense attorneys, Harris, the FBI agent, acknowledged that Rhodes had a habit of popping in and out of the chat with other Oath Keepers and not responding to every message.
Caldwell's defense attorney David Fischer posed a series of questions regarding gun "culture" in the South in which he was met with multiple objections before moving on to ask about Harris' preparation for the trial and the various lengths of time it typically takes terrorism cases to come to trial.
"It depends on what you mean by 'familiar with the South,'" Harris told Fischer, later adding that had not met anyone who hunts for sport since moving to Florida.
Harris acknowledged in the cross-examination that Caldwell was not sending the messages he testified to earlier on Thursday.
The trial could last until mid-November, the judge has said.
ABC News' Alexander Mallin contributed to this report.