Roger Stone allegedly called an associate "a rat" and threatened to have his dog killed in a bid to stop him testifying to the special counsel investigating ties between the Trump campaign and Russia.
Mr Stone, a former adviser to Donald Trump, was arrested in Florida by the FBI on Friday on seven counts involving witness tampering, obstruction and false statements regarding interactions he had with Wikileaks ahead of the 2016 presidential election.
The indictment, brought by special counsel Robert Mueller, details extraordinary interactions between Mr Stone and senior officials in the Trump campaign, as well an two other unnamed high-profile individuals.
Prosecutors accuse the political provocateur of threatening one of the unnamed associates, who hosted a radio programme, in an apparent attempt to stop the unnamed person from testifying to investigators probing Russian influence in the 2016 US presidential election.
The 24-page indictment is peppered with alleged threats from Mr Stone to the unnamed associate:
"You are a rat. A stoolie. You backstab your friends-run your mouth my lawyers are dying Rip you to shreds," Mr Stone told the person in a 9 April email.
He also threatened to "take that dog away from you," and said, "I am so ready. Let's get it on. Prepare to die."
In a 1 December 2017 text message, Mr Stone told the person: "If you testify you're a fool. Because of tromp I could never get away with a certain my Fifth Amendment rights but you can. I guarantee you you are the one who gets indicted for perjury if you’re stupid enough to testify."
In a 21 May email, he wrote: "You are so full of. You got nothing. Keep running your mouth and I'll file a bar complaint against your friend.”
Another 1 December 2017 message referred to a character in the mob movie The Godfather: Part II who declines to testify to Congress after mobsters bring his brother from Italy to the hearing in an apparent threat to the man's safety.
Court papers said Mr Stone told the person to "do a 'Frank Pentangeli.'"
Mr Stone, who has repeatedly said in interviews he was likely to be indicted, appeared at the federal courthouse in Fort Lauderdale, Florida, on Friday, where he was realeased on $250,000 bail.