Really sad that she felt such trauma from doing a civic duty. From what I have read, the new service is only a few months old, but I am not positive of that.
I think it would have been very easy for him to see a psychiatrist every week and keep his inner thoughts hidden. I get the impression (and could be wrong) that he could participate quite like a "normal person" when it suited him or circumstances were easy to handle. If he knew right from wrong and could separate his thoughts, he would be able to present before a psychiatrist/ doctor/counselor and not blab about his deep-seated angers, especially if he had a plan in the works. I doubt he told psych about his computer searches and books, his collections of knives and handcuffs, etc.
JMO
Psychiatrists are supposed to be able to get into someone's head so they can prescribe appropriate anti-psychotic drugs. They should be skilled in doing this even if the patient doesn't want it to happen. If the psychiatrist didn't get into Garland's head, then he/she wasn't doing his/her job.