This story has been updated with a response from a spokesman for Marc Kasowitz.

Marc Kasowitz, President Trump s personal attorney on the Russia case, threatened a stranger in a string of profanity-laden emails Wednesday night.

The man, a retired public relations professional in the western United States who asked not to be identified, read ProPublicas story this week on Kasowitz and sent the lawyer an email with the subject line: Resign Now.

Kasowitz replied with series of angry messages sent between 9:30 p.m. and 10 p.m. Eastern time. One read: Im on you now. You are fucking with me now Lets see who you are Watch your back , bitch.

In another email, Kasowitz wrote: Call me. Dont be afraid, you piece of shit. Stand up. If you dont call, youre just afraid. And later: I already know where you live, Im on you. You might as well call me. You will see me. I promise. Bro.

Kasowitzs spokesman, Michael Sitrick, said Thursday he couldnt immediately reach Kasowitz for comment.

ProPublica confirmed the mans phone number matched his stated identity. Technical details in the emails, such as IP addresses and names of intermediate mail servers, also show the emails came from Kasowitzs firm. In one email, Kasowitz gave the man a cell phone number that is not widely available. We confirmed Kasowitz uses that number.

The exchange began after the man saw our story featured last night on the Rachel Maddow show on MSNBC . We reported that Kasowitz is not seeking a security clearance even though the Russia case involves a significant amount of classified material.

Experts said Kasowitz could have trouble getting a security clearance because of what multiple sources described as a recent history of alcohol abuse. Former employees also said Kasowitz had engaged in behavior that made them uncomfortable.

Since the story was published, his spokesman issued a statement disputing several parts of the story: Marc Kasowitz has not struggled with alcoholism, Sitrick wrote. He has not come into the office intoxicated, attorneys have not had to go across the street to the restaurant during the workday to consult Kasowitz on work matters.

The rigorous background investigation that goes into getting security clearance also considers any information relevant to strength of character, honesty, discretion, sound judgment, [and] reliability.

The exchange of emails Wednesday began at 9:28 p.m. Eastern when the man sent the following message to Kasowitzs firm account.