(CNN) Roger Stone formally apologized Monday for his controversial Instagram posts about federal district court Judge Amy Berman Jackson in a letter filed with the court.

Jackson is overseeing Stone's criminal case in DC District Court.

A photo was posted and then deleted from Stone's Instagram account showing Jackson next to cross hairs, mimicking the scope of a rifle. The cross hairs were in the background of the photo, and not directly over the judge. He later deleted that post, posting the same photo without the crosshairs and then deleted that post as well. In the post, Stone said the judge would be presiding over a "show trial."

"Please inform the Court that the photograph and comment today was improper and should not have been posted. I had no intention of disrespecting the Court and humbly apologize to the Court for the transgression," Stone, a longtime associate of President Donald Trump, wrote in the letter.

The photo appears to come from a conspiracy website that features pictures of others, including former Secretary of State Hillary Clinton and Democratic Rep. Adam Schiff against the same background.

Read More