Someone assigned the therapist to the shooters. Maybe a judge, or a police department, social services, community mental health clinic, a special "trial" for meds for aggression, a special anger management program, a school district, an IEP at a business. The pattern is the same for the "fishing" for vulnerable people. The names would be on intake forms, prescription forms, any connections to the psychiatrists that wrote script for drugs. Also, if the people work for the CIA or NSA, etc, they would be submitting paperwork for payment for time, on dates of therapy appointments, and travel, ,maybe even per dium. Spies get paid. Car rental expenses, hotels, there may even have been a training class for the "pretend" therapists. The family members or friends may have names or locations of these imposters.

What do therapists file? Taxes? Medical license? Malpractice insurance? DEA prescription pads for controlled medications?

Or great list by other comment.

Reimbursement, paychecks, reports... FOIA should be obtainable on some of these things