A Texas man was charged Thursday with threatening to send an FBI agent to jail or “murder” him in the criminal case against President Joe Biden’s son, Hunter Biden, federal prosecutors said.

Timothy Mueller, 43, was accused in a criminal complaint of sending threatening messages across state borders and “influencing, obstructing or retaliating” against a federal officer.

It was not immediately clear whether Mueller, of Fort Worth, had appointed an attorney in the case, which was filed in the U.S. District Court for the Northern District of Texas. Prosecutors refer to Hunter Biden only as “HB,” but the dates of the criminal case against him match those of the president’s son.

According to the criminal complaint, Mueller called an FBI agent who was assigned to investigate Hunter Biden’s laptop on June 11. When the agent hung up, Mueller called again and left a threatening voice message, the complaint alleged. Biden was convicted on June 11 of lying about his illegal drug use in order to buy a gun.

Prosecutors say Mueller accused the agent of covering up crimes committed by Biden and said the FBI agent would go to jail if former US President Donald Trump is elected in November.

“Or you can steal another election, and then the guns will come out, and we will hunt you down and kill you in your own homes, in your own beds, like the traitor dogs you are,” Mueller said in the message, according to the criminal complaint.