Guy Reffitt, who is defending himself against five felony counts for his part in the U.S. Capitol riot last year, listened Thursday as his soft-spoken teenage son took the stand to testify against him in federal court.

The 49-year-old Texan is the first person to stand trial for participating in the deadly Jan. 6, 2021, attack. Prosecutors allege that he was carrying a loaded pistol on the grounds of the Capitol while a mob of Donald Trump supporters attempted to disrupt the formal certification of the 2020 presidential election.

Reffitt, an alleged member of the far-right Three Percenters militia group, threatened to shoot his son and daughter if they talked about his part in the riot after he returned from Washington, court documents say. His attorney has said Reffitt is prone to hyperbole. He pleaded not guilty.

A CBS News reporter at the trial said that the defendant “immediately broke down crying” when he saw his son called into the Washington courtroom.

Jackson Reffitt, 19, said that he and his father had been close until around 2016 and that his father’s rhetoric took an alarming turn following the 2020 election. That paired with his father’s increasing involvement with the Texas Three Percenters ― Guy Reffitt allegedly tossed his son out of their Wylie, Texas, house while the militia met there ― prompted Jackson to send the FBI a tip about his father on Christmas Eve, Politico reported. He said he felt “paranoid” that his father’s talk might lead to violence.

In a Dec. 24, 2020, text exchange shown in court, Guy Reffitt told his son that “what’s about to happen will shock the world.” Jackson watched the storming of the Capitol unfold on television alongside his mother and sister.

He said he secretly recorded a conversation with his father after his return to Texas, testifying that he felt “pretty gross” about the move, according to NBC News reporter Ryan Reilly. In a clip played in court, Guy Reffitt brags about his part in the riot and says a lot of other people around him were also armed but chose not to fire their weapons.

Guy Reffitt later realized his actions might have consequences.

“If you turn me in, you’re a traitor. And traitors get shot,” he recalled his father telling him, according to NPR reporter Tom Dreisbach, adding that he felt “terrified.” The teen moved out of his parents’ house after they discovered he had shared a recording of his father with the FBI, and he raised about $150,000 through a GoFundMe drive to pay for college and car expenses.

Reffitt’s wife, Jodi, told reporters after the emotional day of testimony that she had told her son she loved him earlier in the day.