Dr. Penny Wheeler announced plans Thursday to retire at year's end as chief executive of Allina Health System, ending her seven-year tenure running one of the state's largest networks of hospitals and clinics.

Lisa Shannon will become the new Allina CEO, having served as the nonprofit group's chief operating officer since 2017. Shannon added the title of president in 2020. Wheeler will remain on the nonprofit group's board of directors.

Wheeler's term has been marked not only by a global pandemic and the racial reckoning following the murder of George Floyd — who was killed just blocks from Allina's headquarters — but also the deep pain of personal tragedies for herself and her employees.

In January, Wheeler's 21-year-old daughter died in Iowa, an accidental death that authorities attributed to excessive drinking and exposure to the cold. A little more than two weeks later, a gunman was arrested after opening fire at an Allina clinic in Buffalo, Minn., killing one person and wounding four others.

In an interview Thursday, Wheeler said she told board leaders about 212 years ago that she hoped to retire in a couple of years. The experiences over the past 18 months didn't change the timeline, she said, but deepened the experience of running Allina, including going to visit relatives of those injured in the clinic shooting.

"The daughter of one [victim] was an employee of ours, and she draped herself over me and said: 'I'm so sorry about your daughter,' and I said: 'I'm so sorry about your Mom,' " Wheeler recalled. "It was just like this grief, layered on grief, layered on pandemic. I'll never forget that moment."

With more than 28,000 employees, Allina operates more than 90 clinics and 11 hospitals, including Abbott Northwestern in Minneapolis and United in St. Paul.

A dietician by training, Shannon, 56, said her early clinical work impressed on her the value of inter-disciplinary teams in health care. She worked alongside physicians and other caregivers to tackle questions such as how nutrition can help burn patients recover.

In time, she helped develop programs to promote healthy lifestyles in workplaces. Later, while working for a health system in Ohio, Shannon helped develop an employee wellness and occupational health program for a major automobile manufacturer.

"I'm just so honored to have been selected by the board to continue the strategic plan and continue the commitments that we've made as Allina Health to our community," Shannon said in an interview.

Wheeler started as CEO in 2015. Her early years saw Allina trying to navigate the never-ending financial challenges in health care while dealing with unique issues, such as deciding to close a McDonald's after weathering years of criticism for housing of a fast-food restaurant at its largest hospital.

In 2016, union nurses at Allina went on strike for 37 days during a protracted labor dispute. At roughly the same time, the health system moved to consolidate operations between its Mercy and Unity hospitals in the north metro.

In 2017, Allina launched a health plan in conjunction with insurance giant Aetna. The start-up company was part of a broader push to change the way doctors and hospitals get paid, with the goal of rewarding quality of care rather than quantity of services.

The CEO job intensified in 2020 with the pandemic, and its disproportionate hit to communities of color, followed by Floyd's death in May. Allina had always made it a priority to help, Wheeler said, but the goal suddenly took on new urgency.

Allina called on board members and 100 executives within the organization to go through an "inter-cultural development inventory," Wheeler said, where leaders were challenged to reflect on their own biases. There's now a new system for evaluating Allina's progress toward diversity, equity and inclusion goals, she said, plus renewed pledges to work with communities.

"George Floyd's murder eight blocks away from our headquarters here deepened that," she said. "We have an opportunity now to do the difficult work, have the difficult conversations, to change this community and its health for the better."

The death of her daughter prompted deeper reflections. Wheeler found herself asking if she was leading a life filled with purposeful work. One conclusion she's shared with colleagues, Wheeler said, is that working in health care is one such calling, because it can change lives for the better.

"If anything is going to ring hollow, it's going to ring hollow on the heels of a terrible tragic loss — and this work does not," she said.

Since the shooting at the Buffalo clinic, Allina has committed about $30 million to bolster security across its network of clinics, urgent care centers and hospitals, Wheeler said. That covers everything from security cameras and doors to communication systems.

The Buffalo clinic is scheduled to reopen later this month.

"I think the time is right," Wheeler said of retirement. "The other thing that makes it easy is we have a leader who's ready and has just risen above every challenge that we've had in Lisa Shannon. So I feel really good about who the board has selected as my successor."