On Monday, the FBI raided the home, office, and hotel room of President Trump’s personal lawyer Michael Cohen to seize documents for an investigation into possible bank fraud, wire fraud, and campaign finance violations, according to the Washington Post. The Wall Street Journal reported that the U.S. attorney’s office in Manhattan conducted the raid, at the referral of Robert Mueller’s special counsel’s office, to look into Cohen’s payment to Stormy Daniels, a former adult film star who allegedly was paid to keep her affair with Trump quiet.

Predictably, Trump did not respond well to the news of the raid, and on Monday night before a meeting with military advisers, he struggled to not appear shaken. “So I just heard that they broke into the office of one of my personal attorneys, a good man and it’s a disgraceful situation,” he said. “It’s a total witch-hunt. I’ve been saying it for a long time.”

Again, predictably, Trump’s second round of responses came on Twitter on Tuesday morning.

Attorney–client privilege is dead! — Donald J. Trump (@realDonaldTrump) April 10, 2018

It is uncommon, but not unheard of, for a warrant to be obtained to search an attorney’s office for documents. According to USA Today, prosecutors would have obtained approval for the raid from Deputy Attorney General Rod Rosenstein and have had to establish probable cause to a federal magistrate. And, to get a warrant instead of a subpoena, the prosecutors would have also needed to to show that there was a risk to giving Cohen ample time and opportunity—that he would destroy evidence, for example.

Additionally, the documents they would have obtained would have to relate to Cohen’s possible crimes, not his client’s. And to protect attorney-client confidentiality, a team would examine the documents before they were given to prosecutors to ensure none violated attorney-client privilege (meaning any documents in which Cohen gave legal advice or gathered information in order to give legal advice). If the documents indicated evidence of a crime committed both by Cohen and his client, working together, then attorney-client privilege might not protect them.

A TOTAL WITCH HUNT!!! — Donald J. Trump (@realDonaldTrump) April 10, 2018

The president sure is playing it cool.