The lawyer representing the president of the United States just threatened a stranger in a string of angry and profane emails that included a blunt warning to “watch your back, bitch.”

ProPublica’s Justin Elliott shared the exchange between an unidentified man and President Trump’s personal lawyer Marc Kasowitz. It started when the stranger, a retired public relations professional in the western United States, sent Kasowitz an email late Wednesday night with the subject line “Resign Now” that asked him to “resign from your position advising the president.”

Just five minutes later, Kasowitz responded, “F*ck you.” But it didn’t end there. Without receiving a response from the stranger, Kasowitz launched into an angry and threatening tirade.

Fifteen minutes after his first response, Kasowitz replied again, saying, “Watch your back, bitch.” Here’s the full email:

8/ Then, 15 minutes later, Kasowitz replied again: pic.twitter.com/sw4C1rEh4w — ProPublica (@ProPublica) July 13, 2017

The stranger responded politely, and somewhat sarcastically, soon after, saying, “Thank you for your kind reply.”

Minutes later, Kasowitz then dared the stranger to challenge him to his face — “Don’t be afraid, you piece of shit.”

10/ But Kasowitz continued to harangue him: pic.twitter.com/OHI2eF2ZKj — ProPublica (@ProPublica) July 13, 2017

The exchange ended with another response from Kasowitz, again threatening the stranger and challenging the man to call him. “I already know where you live, I’m on you,” he said.

11/ And then, Kasowitz, the man representing the President of the United States, replied again: pic.twitter.com/hBqqnNAcVO — ProPublica (@ProPublica) July 13, 2017

Yes, this actually happened. ProPublica verified the exchange of emails, and the stranger told ProPublica the whole incident disturbed him so greatly he forwarded the emails to the FBI.

The emails aren’t the only problems facing Trump’s lawyer

Kasowitz is representing Trump as the president and his team are being investigated for obstruction of justice and possible collusion with Russia. And as Vox’s Alex Ward and Rebecca Tan reported, Kasowitz and his small team already seemed outmatched when compared to the experienced lawyers and investigators working for special counsel Robert Mueller:

Trump’s team, by contrast, is led by Marc Kasowitz, a Wall Street lawyer with minimal experience in federal investigations who burst onto the national scene with a typo-ridden statement defending the president. His top two partners so far, Michael Bowe and Jay Sekulow, are known more for their time on TV than their time in the courtroom, and don’t have anywhere near the background Mueller’s team boasts to take on this challenge. It’s also not looking like Kasowitz’s team is going to get much stronger anytime soon. Prominent lawyers with investigative experience at four major law firms declined to represent the president, citing concerns about Kasowitz’s leadership and influence over Trump. These lawyers include Brendan Sullivan of Williams & Connolly, a white-collar specialist who is consistently named as one of the top 100 trial lawyers in the country, and Ted Olson of Gibson, Dunn & Crutcher, who was the solicitor general under George W. Bush from 2001 to 2004.

Kasowitz has also rankled some in the White House by reportedly bypassing White House counsel Don McGahn and sparring with Trump adviser Jared Kushner, himself a target of several of the probes.

Recently there have been reports that Kasowitz could be denied a security clearance, something he needs in order to access classified government information and continue working closely with Trump.

There may be a reason for that, and it’s a serious one: ProPublica spoke with more than two dozen people close with Kasowitz for a recent article who said that he has a history of intermittent alcohol abuse and spent time in rehab in the winter of 2014-’15.

A spokesperson for Kasowitz angrily denied the report, telling Law.com that Kasowitz “has not struggled with alcoholism” and that “much of what [ProPublica] reported is false and defamatory.”

But regardless of what caused the outburst, this email exchange offers a new and disturbing glimpse into the mindset of the person charged with protecting Donald Trump. That would be a tough job for any lawyer. It seems it may be even harder for this one.