After Trump tried to fire the Special Counsel through White House Counsel Don McGahn, Trump later directed McGahn to put in writing that the request had never been made. The President remarked, “if he doesn’t write a letter, then maybe I’ll have to get rid of him.” McGahn refused, and though Trump backed down from his threat, McGahn ultimately resigned.

McGahn noted that during his tenure, he had been asked to “do crazy shit.”

The Special Counsel originated in an FBI investigation into Russian interference in the 2016 election, and officially formed after Trump fired FBI Director James Comey.

US Department of Justice – Report On The Investigation Into Russian Interference In The 2016 Presidential Election (The Mueller Report), pages 86, 115-118
The Hill – Mueller tells House panel Trump asked staff to falsify records
NBC News – Mueller report found Trump directed White House lawyer to ‘do crazy s—“