Donald Trump’s chief private attorney seems to be very thin-skinned.

On Wednesday night, Marc Kasowitz sent a series of profane and threatening emails to a critic who urged him to resign as Trump’s lawyer in the ongoing Russian investigation. It all started after the critic, who asked not to be identified, sent an email to Kasowitz with a subject line that simply read: “Resign now.”

According to ProPublica, the sender contacted the lawyer after watching an episode of MSNBC's The Rachel Maddow Show that discussed a recent ProPublica story about Kasowitz. The report cited several sources who claimed Kasowitz’s history of alcohol abuse was preventing him from getting security clearance. So the unidentified critic decided to express his concerns and offer Kasowitz a suggestion:

“You don’t know me. I don’t know you,” the email starts out. “But I believe it is in your interest and the long term interest of your firm for you to resign from your position advising the President re. pending federal legal matters," the man wrote. "No good can come from this and in fact your name may turn out to be a disparaging historical footnote to the presidency of DJT.”

Kasowitz response? “F*ck you.”

The man clearly wasn’t happy with the message, but he wasn’t done giving the critic a piece of his mind. Kasowitz went on to send several more profanity-laced emails with some threats sprinkled in, such as: “I’m on you now. You are fucking with me now Let’s see who you are Watch your back , bitch”; and “Call me. Don’t be afraid, you piece of shit. Stand up. If you don’t call, you’re just afraid”; and “I already know where you live, I’m on you. You might as well call me. You will see me. I promise. Bro.”

ProPublica was able to verify the authenticity of the emails by identifying IP addresses and names of intermediate mail servers, both of which were tied to Kasowitz’s firm. The publication also confirmed that the phone number Kasowitz provided in one of the messages is, in fact, his.

The recipient forwarded the emails to the FBI; however, it is unclear if the lawyer will be in any legal trouble.

A spokesperson for the attorney reached out to ProPublica, insisting Kasowitz intends to issue an apology:

Mr. Kasowitz, who is tied up with client matters, said he intends to apologize to the writer of the email referenced in today’s ProPublica story. While no excuse, the email came at the end of a very long day that at 10 p.m. was not yet over. ‘The person sending that email is entitled to his opinion and I should not have responded in that inappropriate manner,’ Mr. Kasowitz said. ‘I intend to send him an email stating just that. This is one of those times where one wishes he could reverse the clock, but of course I can’t.

You can read the email exchange in screenshots provided by ProPublica below.