EUGENE, Ore. -- Students, staff and alumni at the University of Oregon are outraged after a law professor wore blackface to a Halloween party.

Photos surfaced after professor Nancy Shurtz wore the costume at a private party

UO president Michael Schill sent an email to students and staff condemning the costume.

"The use of blackface, even in jest at a Halloween party, is patently offensive and reinforces historically racist stereotypes," the letter reads. "It was a stupid act and is in no way defensible."

Some students and alumni have started a petition asking for Shurtz to resign.

Shurtz sent a letter to her students explaining that the costume was based on a character from a book she read, and she thought she could "teach with this costume...or at least tell an interesting story."