[livius]

The difference is that the Orlando shooter didn’t do it because he thought his religion was telling him to. There will always been crazy people who decide to “resolve” a workplace (in his case) or a marriage or other dispute by killing everybody around them. But on your list, all the others - the Muslims - did it because of their religion, and they said so at the time.

[Star Traveler]

I am aware of the Islamo-fascist governmental idealogy (that many call Islam) designed to take over the world under a one-world government using terror and killings to help carry out the deed.

And while that part may be true, mass shootings have still been going on here in the U.S. for a long while now (along with a goodly number of individual shootings, that get a whole lot less press coverage).

I’m afraid that we’re killing off each other, in this country, a whole lot faster than the Muslims are able to do it — in this country (including what was done on 9/11).

[Steve Van Doorn]

Or you can say:
When a Muslim commits mass murder we can not tell if it is an act of insanity or if he/she was practicing their religion.