Olga Viso is stepping down as executive director of the Walker Art Center after a challenging year marked by the debut of a colorful new campus and searing protests over a controversial sculpture.

In a surprise announcement Tuesday, the Walker said Viso, who has led the internationally known center since 2008, will leave by year end.

Four sources close to the board characterized her resignation as the end result of a monthslong process fueled by unusually high turnover among Walker staff and demonstrations against the “Scaffold” sculpture that delayed the gala opening of the Minneapolis Sculpture Garden last spring.

The departure is “Olga’s decision,” said Walker spokeswoman Rachel Joyce, but the board is “in strong agreement that the timing is right. Olga certainly feels that way.”

The June reopening of the expanded garden, paired with a $75 million capital and endowment campaign, was supposed to be Viso’s shining moment. Instead, it became the focus of anger from the American Indian community, with some calling for her resignation over “Scaffold,” a sculpture modeled partly on the gallows used to hang 38 American Indians in Mankato after the U.S.-Dakota War of 1862.

Viso apologized, met with Dakota elders and agreed to the dismantling of the work. The Walker board then ordered an independent investigation of the internal process around “Scaffold”; results of that review have not been disclosed.

Walker Art Center director Olga Viso.

“We are grateful for Olga’s leadership and celebrate her significant contributions to the Walker Art Center during the past 10 years,” Walker board President Monica Nassif said in a statement Tuesday. “She led the organization through a major capital campaign to fund the vision and redesign of our entire campus, including the new Minneapolis Sculpture Garden.”

Nassif and Viso did not respond to requests for comment Tuesday.

The Walker said its board will form a search committee to hire a new director. Viso’s salary was $496,355 in 2015, according to the Walker’s most recent public tax filing.

In the interim, the center will be led by four senior staffers as a collective “chief executive” — chief advancement officer Christopher Stevens, chief financial officer Mary Polta, senior curator Siri Engberg and human resources director Rishi Donat.

In a statement, Viso said: “It has been a privilege to lead this venerable contemporary arts institution the last 10 years and to support the work of some of the most compelling and adventurous international artists working today.”

“Completing the vision for the campus that began in 2005 with the Walker’s Herzog & de Meuron addition has been an absolute highlight. I am immensely proud of what we — the Walker’s talented and ambitious staff and the generous community of donors who stepped up boldly — have accomplished together.”

Tensions with board

Board members could not comment on Tuesday’s announcement because they have a nondisclosure agreement with Viso, according to sources close to the 44-member board.

One characterized the split as “an amicable divorce.” They pointed to long-simmering tension between Viso and the board over what some describe as her tough and demanding management style, which contributed to the departure of several senior leaders.

At the same time, they said, the board credited Viso for her vision — including the new Walker campus, with a much-praised entrance and restaurant facing the Sculpture Garden — along with the successful capital campaign and her recovery from “Scaffold.”

Staff rumblings first became public two years ago, following the resignations of seven top curators and department heads. More questions were raised last January when Fionn Meade, who in 2015 was elevated to the new post of artistic director, resigned abruptly for undisclosed personal reasons.

In a recent interview, Meade predicted that “Olga’s legacy will be tied to the success of the Sculpture Garden and the Walker campus,” which he called “a visionary success and I admire her for it.”

But, he said, “it came at a cost” — burnout and low morale that led to the departure of more than two dozen staff members since last December. Meade faulted Viso for failing to hire sufficient staff to complete the campus project while maintaining an ambitious exhibition schedule.

“That cost is still happening,” he said. “And the institution, in terms of staff, will take a long time to recover.”

Her final ‘passion project’

Viso spent last weekend celebrating with Cuban artists and Walker staff and supporters gathered for the opening of “Adiós Utopia,” an exhibit that the Walker director — herself the Florida-born daughter of Cuban émigrés — described as a “passion project.”

In May, Walker Art Center director Olga Viso watched as Sam Durant, the artist behind the "Scaffold" sculpture, spoke during a Q&A.

Smiling as she worked the crowd at Friday’s opening party, she gave no indication that the show of Cuban art was, in essence, her swan song.

Before coming to the Walker, Viso was director of the Hirshhorn Museum and Sculpture Garden in Washington, D.C., where she was praised by the Washington Post for her “commitment to experimental, even difficult” art.

In retrospect, that commitment led to her misstep with “Scaffold,” the work by Los Angeles-based artist Sam Durant that she spotted at an event in Germany in 2012 and championed as one of 18 new works for the sculpture garden.

“I saw a potent artistic statement about the ethics of capital punishment,” she said in an open letter last spring that touched off the public debate. “Most importantly, I recognized its capacity to address the buried histories of violence in this country, in particular raising needed awareness among white audiences.”

Reflecting on the episode recently, Viso said she intended the piece to reveal a history too few Minnesotans know, and didn’t anticipate the trauma it would trigger.

“I understand what it means to be misrepresented, to be misunderstood,” she said. “I’m someone who’s deeply committed to respecting culture … and institutionally, the Walker is as well. So that we would misstep is even more painful. It’s not who we are.”

Tuesday’s statement noted that the Walker’s board became significantly more diverse during her tenure. Currently, 20 percent of its members are people of color, compared with 5 percent in 2008.

Board chair Nassif told the Star Tribune last month that the Walker’s investigation was prompted by the mediation process that led to the dismantling of “Scaffold.” The center’s leaders, she said, “agreed to examine our institutional structures and policies and work to make structural change.”

While the report, by Minneapolis firm Nilan Johnson Lewis, has not been made public, Nassif said the board already had drawn one conclusion: “With works going into public spaces … we need to add another level of consideration.”

Staff writer Alicia Eler contributed to this report.