Three of Philadelphia Mayor Michael Nutter's senior staff members will be stepping down. 

The mayor announced the administrative changes Friday at City Hall.

Leaving are Dr. Donald Schwarz, health commissioner and deputy mayor for the Office of Health and Opportunity; Ann Marie Ambrose, who leads the Department of Human Services; and Suzanne Biemiller, the mayor's first deputy chief of staff.

Schwarz has been recognized for his efforts in housing for the homeless, as well as obesity and anti-smoking initiatives and early childhood education, during his six years in City Hall.

Ambrose, who also has been with the Nutter administration since 2008, took over the Department of Human Services in the wake of scandal over the case of 14-year-old Danieal Kelly, who starved to death.

Ambrose quickly overhauled the city's child welfare agency, introducing a new case-management system; in 2013, her department received the United Nations Public Service award, the only organization from North America selected.

"I'm going to miss them enormously, but they have lives, they have talent, and I'm always proud when my folks are able to do something else or go onto greater heights," said Nutter. "The fact of the matter is that I recruited them from somewhere else, they're talented people, and there's no surprise that others would recognize that talent and then subsequently recruit them."

Both officials are moving to new jobs — Schwarz is headed to the Robert Wood Johnson Foundation while  Ambrose will be joining Casey Family Programs.

Biemiller is leaving to serve as chief of staff for the American Board of Internal Medicine.

All three were teary-eyed as they thanked the mayor Friday during the press conference.

"He has been unwavering in his support and commitment," said Ambrose. "All he's ever said to me was 'Do the right thing for kids, I've got your back,' and he has had my back for six years."

Ambrose's deputy, Vanessa Garrett Harley, will take over as commissioner of Human Services in mid-July.

Susan Kretsge, chief of staff in the Office of Health and Opportunity, will take over as deputy mayor for Schwarz.

Nutter appointed Dr. James Buehler, a Drexel University public health professor, as the new health commissioner.

The mayor anticipates a smooth transition.

"This is all highly talented leadership that will not miss a beat and will keep marching forward providing high quality service for the citizens of this city," said Nutter. "I'm very proud of them, very sad, but confident going forward as life moves on."