Depends what your objective is. If your goal is to accelerate political violence and set Americans at odds to an even greater degree than they already are, it's completely rational. I have no idea who did it; it could be domestic extremists, foreign actors, cynical strategists. It might be some isolated murderous person with a chip on their shoulder who totally hated Kirk, but that seems like the least likely possibility because of the fact that they've made a clean getaway - 12 hours with no CCTV imagery or even a good description is unusual for such a public event.