Well, guns clearly make it worse. Had the Batman shooter had a hammer instead of a gun with a 200 round magazine there would have been far fewer casualties, and stabbing/hammering someone is certainly more visceral and harder to do than merely pulling a trigger (I'd wager most of these people are too cowardly to do that.)
But yes, it'd still be happening, just with fewer casualties and likely fewer incidents as a whole.
And it's amusing that you're saying religion would solve this. I'm pretty certain there's an area in this world full of religious bombings that would disagree wholly, as well as a few periods of history full of religious inquisitions and crusades that would also disagree.