Pop the magnetron out of a microwave and direct it towards someone's head [0], and I imagine they're not gonna have a great time. And that's with parts available in many average homes.
The Active Denial System [1] works based on these principles, but different frequencies.
Mount that magnetron in front of an ordinary satellite dish and oh boy whatever is at the focal point of it will not have a nice day either. Your average satellite dish has about 38 dBi of gain - an 1 kW magnetron will yield something around 3 MW EIRP if you manage to end up in the RF path.
That is why even around "small" scale radio transmitters such as phone cell towers you absolutely have to keep a safe distance, and even more around large broadcast towers or even radio amateurs doing serious satellite communication.
The concept is the same: directed radio waves. They can be tuned and directed far better than a magnetron and waveguide pulled from a microwave. This is an adversary more sophisticated than some rando disassembling appliances in their garage, and even a moderately knowledgeable radio technician could improve upon it.
For it to do enough damage to make the inner ear fail temporarily and give you brain damage without burning anything seems a bit unbelievable though. Not even a first degree burn? I think even something as unlikely as remote-activated poison is a better explanation.
Different frequencies interact differently with wall materials or window materials or hydrous, organic matter. For example, many substances are pervious to microwave radiation and will remain cool while an egg beneath them cooks.
This is true for your skin in some cases, too: the frequencies which will quickly heat skin are a subset of the frequencies which can hurt you at high energy. For example, X-rays will do the latter a lot faster.
And that's only the considerations if you treat the skin and brain as just a hunk of stuff versus a ridiculously complex meat-computer. For an example, see the "microwave auditory effect"[0]. This effect originates inside the brain, not the ear. High levels of electromagnetic energy tends to harm even electronic computers, and they have no meat to deal with!
That's actually something I didn't think about! So the EM wave don't interact with the liquid, but the brain electric signal. I don't know if it is possible, but it is a far, far more likely than something that fry the inner ear/brain.
Ok, I'd rank it ahead of the poison theory, still behind the mass psychosis because of Hanlon though.
