You do realize the from the perspective of groups such as Muslim Brotherhood, Hamas, ISIS, or Al-Queda (not to mention the Shiite regime in Iran), the Mamdanis would be considered extreme heretics worthy of execution.
And since attack was by private citizens on other private citizens, it doesn’t raise constitutional issues, since the First Amendment only restricts the government (it would be assault with intent to kill, and perhaps acting as an unregistered agent of a foreign power).