Harry L. Gillin, 32, data analyst and volunteer

In the summer of 2001, before he was to enter his senior year at St. Joseph's Prep in Philadelphia, Harry L. Gillin and a half dozen of his classmates took a car trip.

They went to teach and work with Navajo boys and girls, ages 8 to 14, at St. Michael Indian School, in the Arizona portion of the Navajo Nation.

"Our goal was to teach," said Bill Conners, a history teacher at St. Joseph's who led the annual two-week visit, "but we all agreed they learned much more than they taught."

Mr. Gillin, Conners said, "was always willing to challenge himself."

On Wednesday, Oct. 12, Mr. Gillin, 32, a former staffer in the development office at the University of Pennsylvania, died of cancer of the appendix at his parents' home in Gloucester Township.

Born in Lower Merion, Mr. Gillin graduated from St. Joseph's Prep in 2002, earned a bachelor's in political science at Loyola University Maryland in Baltimore in 2006 and a master's in government administration at the Fels School at Penn in 2009.

Mr. Gillin was a staffer from 2007 to 2013 in the Office of Development and Alumni Relations at Penn, said a sister, Deirdre Ruttle.

Since 2014, she said, he had been a data analyst in the Philadelphia office of Sonepar USA, a distributor of electrical and safety equipment.

Conners, the St. Joseph's teacher, recalled that, as a sophomore, Mr. Gillin was his student in American history studies.

"In our classes," Conners recalled, "we had studied a lot about Native Americans," and so the trip to Arizona "was a chance to see in real life what we learned in the classroom."

The Prep students taught on one day, he said, "and the next day we would work on projects, whatever they needed us to do. Back and forth."

As outsiders, they also ran the equivalent of a two-week summer camp for the Navajo youngsters.

"He was a curious kid," Conners said of Mr. Gillin. "He had a great sense of humor."

Mr. Gillin also took time more recently for charitable efforts, his sister said, rebuilding homes, for a few weeks in 2011 and again in 2012, for Habitat for Humanity in New Orleans.

Besides his sister Deirdre, Mr. Gillin is survived by his parents, Eugene and Elizabeth, and a sister, Kayla Gillin.

A visitation was set from 6 to 9 p.m. Monday, Oct. 17, at the Church of the Gesu, near 18th Street and Girard Avenue, in Philadelphia, with a Funeral Mass set for 9:30 a.m. Tuesday, Oct. 18, at Old St. Joseph's Church, 321 Willings Alley in Society Hill.

Donations may be sent to the Development Office, St. Joseph's Prep, 1733 W. Girard Ave., Philadelphia 19130.

Condolences may be offered at helwegrowlandfh.com.

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