NEW : Defense Secretary Gates : Leaks should stop , because they might jeopardize probe . Medical school classmates : Hasan espoused Islamist views in class . He was a Muslim convert who converted to Islam after his wife died of cancer. Hasan charged with murder , accused of killing 13 at Fort Hood last week .
NEW : Defense Secretary Gates : Leaks should stop , because they might jeopardize probe . Medical school classmates : Hasan espoused Islamist views in class . Hasan said his allegiance was to Sharia law , not the U.S. , source says . Hasan charged with murder , accused of killing 13 at Fort Hood last week .