An Egyptian court has convicted three Islamists of killing a student this summer as he sat in a quiet park with his fiancee, sentencing them to 15 years in prison in a case that sparked fears of vigilantes trying to enforce strict religious mores.

The state-owned Middle East News Agency said the Tuesday verdict was read out in a heavily-guarded courtroom in the Red Sea city of Suez, where 20-year-old Ahmed Hussein Eid was killed in June. According to security officials at the time, three bearded men argued with Eid for loitering in the park with a woman who was not his wife. One fatally stabbed him.

Many in Egypt fear that the rising political power of ultraconservative Islamists will see them flexing their muscles on the streets as well.