Atkinson has been charged with violating laws governing interstate communications, which prohibit “any threat to kidnap any person or any threat to injure the person of another” and is punishable by up to five years in prison.

The indictment follows months of rhetorical salvos by the president and his allies against the whistleblower, whose purported identity has been posted on social media and even read aloud in the Senate chamber despite federal laws that allow whistleblowers to remain anonymous in order to encourage them to report wrongdoing.

Trump has tweeted about the whistleblower more than five dozen times since September, accusing the person of being part of the “deep state” and alleging that he gave the Intelligence Community inspector general false information. Nothing in the whistleblower’s original complaint, however, has proven inaccurate.

Zaid and his co-counsel on the whistleblower case, Andrew Bakaj, wrote a letter to then Acting Director of National Intelligence Joseph Maguire in September raising “serious concerns” about their client’s safety following remarks Trump made at the U.N. accusing the whistleblower of being a “spy.”

“You know what we used to do in the old days when we were smart with spies and treason, right? We used to handle it a little differently than we do now,” Trump said, according to audio of the remarks obtained by The Los Angeles Times.

To Zaid’s knowledge, the indictment is the first time an individual has been charged with making death threats against him, he said. But it’s far from the first threatening email he and his legal partner Bradley Moss have received since taking on the whistleblower as a client.

“@realDonaldTrump thank you so much for the specific commentary about my firm last night,” Moss tweeted on November 7, the day Atkinson allegedly threatened Zaid. “I woke up to a ton of hate mail and death threats. And I’m not even on this case.”

"It's not appropriate for anyone to threaten another individual's life, regardless of political views," Zaid said. "My job was to ensure the rule of law was followed in how whistleblowers are treated. That role should not be negatively weaponized by partisans."

"I hope this indictment sends a message to others that such behavior will not be tolerated by a civil society that is governed by law," he added.

Whistleblower protection advocates and national security experts have warned that the president’s attacks on the intelligence community employee who first raised alarms about Trump’s call with Ukraine’s president last summer could lead to violence.

The issue of whistleblower protection was a central focus of the intelligence community inspector general Michael Atkinson’s confirmation hearing two years ago, where he pledged to establish “a safe program where whistleblowers do not have fear of retaliation and where they’re confident that the system will treat them fairly and impartially.”

Seamus Hughes, the deputy director of the Program on Extremism at George Washington University, first noticed the recently unsealed indictment.