He was still sober enough to crack the real cause that the ultra-low frequency was capable to affect the brain from the outside. That was why he disregarded an initial idea of the microwave. Although, there was another possibility that the manipulator told him it was an ultra-low frequency deployed during the manipulation.
It is quite rare that the perpetrator realized or claimed he was a subject of the electromagnetic manipulation. There was one murder case in Japan and that is also highly likely a result of the same operation.
In the most of the cases, the perpetrator heard the voice but could not identify what it was. They have often claimed those were voices from the GOD, the devil or the inner self, which pushed them to commit crimes.
62 [Electromagnetic wave and Ghost]: A bird suddenly appeared and smashed a window with an invisible voice
You can choose whichever, but most of us prefer to say that it is a result of the mental illness. On the other hand, it is quite rare that the mental illness persists to tell the perpetrator to kill a specific target or in a specific way, as it is not an obsession or paranoia but a voice. The electromagnetic wave is a more probable answer of those as a matter of fact.
However, there was a big problem in his case. He even realized the real cause, while he held guns in any way and shot many innocent people. He believed he fought against the culprits, but it was less likely as they just hid out not to show the real identity to be attacked. He was just brainwashed to become a killer to shoot the wrong target.
The brainwash through the electromagnetic wave is too forceful to resist. It was true to my case and I had been brainwashed to attack the police headquarter for more than six months. I was pretty much sure that I was manipulated externally, but still, my mind had been escalated to attack them.
3-200 [Brainwash to assault the police]: Spy brainwashed me to assault the local police headquarter, failed though
I was lucky enough not to become the perpetrator but are there any general ways to prevent this from happening, not to be brainwashed?