Norman Rockwell’s family has joined the growing list of critics of the Berkshire Museum’s plan to sell off 40 works of art—including two of Rockwell’s most famous paintings—at Sotheby’s next month.

Three generations of the American painter’s relatives met with officials from the Massachusetts attorney general’s office last week in a bid to stop the institution from selling Shuffleton’s Barber Shop (1950) and Shaftsbury Blacksmith Shop (1940), according to the Berkshire Eagle.

Family members brought along a 1958 letter that the Berkshire Museum’s former director wrote to Rockwell, which they believe proves that the artist wanted his works to remain accessible to the public. (The former director, Stuart C. Henry, wrote that the museum was “delighted to have” Shuffleton’s Barber Shop “for our permanent collection.”)

The two paintings—donated to the museum by the artist himself—are estimated to sell for between $27 million and $40 million. They are expected to generate more than half of all proceeds from the museum’s planned sale of 40 works.

“It’s totally against what Norman Rockwell would have wanted,” the artist’s granddaughter-in-law Margaret Rockwell, who manages the Norman Rockwell Family Agency, told the Berkshire Eagle of the sale. “We’re horrified this is happening.”

In August, the Massachusetts attorney general’s office launched an investigation into the institution for possibly violating state laws that govern the deaccessioning of material donated to nonprofit institutions.

Margaret Rockwell told the Berkshire Eagle that she wrote to the Berkshire Museum’s director Van Shields twice on behalf of the family to request paperwork detailing the terms of the artist’s donations, but received no reply. (A spokesperson for the museum has said it is cooperating with the attorney general’s review. A representative did not immediately respond to artnet News’s request for comment on the Rockwell family’s claims.)

The Berkshire Museum has said that the sale of the artworks—which is expected to raise as much as $68.6 million—is necessary to fund essential renovations of its 114-year-old building and to rebrand itself as a mixed-use art and natural history museum, which will ensure its future viability. Since news of the sale was first announced in July, the museum has found itself at the center of a national debate over deaccessioning.

Rockwell’s family hopes that the Massachusetts attorney general will intervene, although it’s unclear if the officials have the legal authority to stop the sale.