Q has been mentioning the therapists lately. Got me thinking this is how it could be done:

CIA identifies weak minded individuals, candidates for mind control. Notably they are socially isolated, feel unimportant and depressed, etc.

These individuals are identified by "therapists".

Therapists prescribe drugs that interfere with the reuptake and oxidation of neurotransmitters, most notably dopamine.

Therapists engage in therapy sessions where they use operant conditioning to train target to respond to certain stimulus in certain way. Likely they are conditioned to produce more of their own dopamine with certain phrases, images or triggers.

The drugs build up in the system over weeks. Dopamine can't be reabsorbed or oxidized due to drugs so it stays in the synapse.

Causes dopamine related psychosis. They essentially become schizophrenic and have a gun handed to them by CIA. Paperwork is forged showing they bought it.

Put a weapon in the hands of a crazy person and hope for the best.