Incidentally, the Washington Post’s headline makes it sound as if a non-Mulsim is stabbing Muslims:

Police: Man stabs two after asking if they are Muslim

People objected to that deliberately-misleading headline, so they’ve changed it to a slightly different lie:

Police: Muslim man stabs two after discussion about religious beliefs

They did not have a “discussion about religious beliefs.” He asked people if they were Muslim and, upon learning they were not, attacked them in accord with the teachings of his religion.