For Jeff Koons’s latest sculpture, the artist has used an unusual material: Guns. And not just any guns, but the gun collection of two-time Academy Award-winning actor Sean Penn.

About six years ago, “Sean informed me that he wanted to decommission his gun collection, and asked if I would have any interest in creating an artwork out of his guns,” Koons wrote in an Instagram post that unveiled the finished work, titled Uli. “I told him, ‘Absolutely.’”

Penn, now 59, made the decision to give up his guns at the behest of fellow Oscar-winning actor Charlize Theron, whom he dated from 2013 to 2015. (The 44-year-old South African actress’s anti-gun beliefs were formed as a teenager, when her abusive father drunkenly shot at her and her mother. Theron’s mother fired back in self-defense and killed him.)

“I’m a self-proclaimed alpha male who owns 67 firearms,” Penn told a star-studded crowd at his 2014 “Help Haiti Home Gala” in Beverly Hills, as reported by the Daily Mail. “But I’ve had my mind changed about guns by a strong woman, a beautiful South African woman.”

To illustrate his new commitment to a gun-free lifestyle, Penn auctioned off the entirety of his collection for the Haiti relief charity. “Koons will decommission [and] render inactive all of my cowardly killing machines,” he announced. “The highest bidder gets every single one of my guns put in the hands of this iconic artist and sculptor.”

Journalist and CNN anchor Anderson Cooper placed the winning bid, edging out then-colleague Piers Morgan at $1.4 million. (This was actually kind of a steal, considering that Koons is among the world’s most expensive living artists, having last year seen his Rabbit sculpture sell for $91 million at Christie’s New York.)

Jeff Koons poses in front of Bouquet of Tulips next to the Grand Palais on October 4, 2019, in Paris. Photo by Thierry Chesnot/Getty Images.

At the time, Koons said on Twitter that it was “very meaningful” to work with Penn on the Haiti fundraiser. The artist tagged Penn’s charity, Community Organized Relief Effort, or CORE, in his Instagram post sharing the new sculpture with the world.

The finished artwork is made entirely of gunmetal, fusing together each firearm into a dark totem-like statue. Koons says he was inspired by the Uli fertility statues traditionally made by the natives of New Ireland in Papua New Guinea.

“Uli figures are normally made out of wood,” he explained. “They represent the maternal and paternal spirit of tribal leaders.”