Two days after the Capitol riot on Jan. 6, Jackson Reffitt’s father, Guy W. Reffitt, returned to the family’s home in Texas. He told his son that he had stormed the Capitol, according to an F.B.I. affidavit.
Then his father leveled a threat: If Jackson, 18, reported him to the police, he would have no choice but to do his “duty” for his country and “do what he had to do.”
In interviews with investigators, Jackson Reffitt said his father told him: “If you turn me in, you’re a traitor. And you know what happens to traitors. Traitors get shot.”
But he had already reported his father to the F.B.I. weeks before the riot.
“He would always tell me that he’s going to do something big,” the younger Mr. Reffitt said in a phone interview on Saturday. “I assumed he was going to do something big, and I didn’t know what.”
Guy Reffitt’s wife told investigators after the riot that he was a member of the Three Percenters, a far-right militia group, according to the affidavit.
F.B.I. agents found an AR-15 rifle and a pistol at his home. The elder Mr. Reffitt told investigators that he had brought the pistol with him to Washington.
Jackson Reffitt said he learned that his father was headed to Washington the day before the riot but that he did not know what he would be doing there. He discovered what was happening when he saw images of rioters storming the Capitol on the news.
It was not clear what, if anything, the Federal Bureau of Investigation did after Mr. Reffitt first contacted the F.B.I. about his father. Federal investigators contacted him during the riots to follow up on his tip from weeks earlier, at which point, he said, he helped “prove what they were trying to investigate.”
Mr. Reffitt said he had “just wanted someone to know” about his father’s threats of “doing something big.”
“I didn’t know what he was going to do, so I just did anything possible just to be on the safe side,” he added.
The elder Mr. Reffitt, who was arrested on Jan. 16, faces charges of obstruction of justice and of knowingly entering a restricted building or grounds without lawful authority. He could not be reached on Sunday, and it was not immediately clear whether he had a lawyer. The F.B.I. was not immediately available for comment on Sunday.
Mr. Reffitt said he was unsure if his father knew yet that he had reported him to the federal authorities.
“I am afraid for him to know,” he said. “Not for my life or anything, but for what he might think.” But he said he was hopeful that his relationship with his father could be repaired.
“We’ll get better over time,” he said. “I know we will.”
He said his mother and two sisters “had no idea what I had done” until they saw a CNN interview he did with Chris Cuomo.
After the interview gained traction online, Mr. Reffitt said on Twitter, “Yes I’m the kid on cnn.”
The tweet garnered thousands of likes and retweets, and he said he was flooded with messages asking him to set up a GoFundMe, so he did.
“Every penny is another course in college or me saving it for years to come,” he wrote on the crowdfunding platform. “I might be kicked out of my house due to my involvement in my dad’s case, so every cent might help me survive.”
Mr. Reffitt was not staying at his family’s home, and he declined to say where he was for fear of his safety. He was using his girlfriend’s phone because his family had disconnected his, he said.
He said he posted the GoFundMe page shortly before going to bed on Friday, expecting a few thousand dollars would be raised. When he woke up on Saturday, the page had raised more than $20,000.
As of Sunday afternoon, more than 1,800 donations were pledged, amounting to more than $58,000.
Mr. Reffitt is in his first semester studying political science at Collin College, a community college near his family’s home in Wylie, Texas, a Dallas suburb. When asked if the money would cover the rest of his undergraduate education, he said: “Oh man, you have no idea. I’m going to go on to a university now.”
As for others grappling with whether to come forward about someone they believe could be involved in something dangerous, “you’re not just protecting yourself, but you’re protecting them as well,” he said.
“I put my emotions behind me to do what I thought was right,” Mr. Reffitt said of reporting his father. And though he does not regret his decision, he said, “He’s still family, and it’s still weird.”