“...brainwashing was at work here.”
That would be from MSM, Antifa, etc. Ever consider that MKULTRA is now propagated wholesale by the MSM and their affiliated socialist groups?
Socialism is violence. Look everywhere it’s present and who advocates it. Violence, assassinations and revolutions.
MKULTRA brainwashing was designed to make the subject forget who brainwashed them and then forget why they did what they did.
If the shooter had lived he probably would not even know why he was at the site or how he got there.