We have to keep saying "they" because nobody knows who did it. Cuba has denied any and all involvement. Attacking official foreign diplomats would violate the Geneva Convention, which is what the global relations community refers to as a "bad idea." But officials don't have any other compelling suspects. A few Canadians experienced attacks as well, which throws a new wrench in the gears. Everybody hates Americans, but Canadians? We're pretty sure their national motto is "No grudges, buddy."
Once officials examined the injuries, things somehow began to make even less sense. The people who never heard anything -- they became nauseous alone, with no accompanying noise -- fit with our current understanding of sonic weapons. But the laser-precise attacks which made a noise are doing things to people which we didn't know was possible. Some have experienced concussions and hearing loss, which is out of the norm for this sort of attack. But others can no longer remember specific words. Somebody is out there with a gun that can erase thoughts out of your head, like Cuba is a level in a fucking Ratchet & Clank game.