KABUL, Afghanistan — In indignant tones, the Islamic law student told her family about the superstitious practices she had witnessed earlier that day at a historic shrine in Kabul.

She had seen illiterate mullahs sell good-luck charms and visitors who were convinced that prayers offered in the shrine were bound to come true.

Over a family dinner, the student, a 27-year-old woman named Farkhunda, vowed to return and speak out against what she deemed superstitious and un-Islamic behavior.

That decision — and what awaited her at the shrine — has convulsed Kabul.

When she returned there last week and began chastising people for their ignorance, an attendant at the shrine countered with a far more dangerous accusation: This woman, he shouted, was an infidel who had burned the Quran. A sparse crowd quickly became a mob of hundreds, and the men railed at her, beat her, set fire to her body.