I have a feeling this is going to be some kind of hate crime...the killer obviously snapped and targeted the clinic as a source of his problems. I find it interesting that the clinic had multiple patients there at the same time. Leads me to believe that it was a walk-in clinic for anyone who feels they need help. Type of place that makes a great out when there is work to be done. I’ll even bet the patients did not have to go through their chain of command before going to the clinic. Can you imagine if we had these clinics in England in May 1944...they would have been full.
The article said he had been brought there by an armed escort. He caused a disturbance at the clinic and the escort was taking him back to wherever he had been brought from. But when Russell got into the vehicle, he overpowered the escort, took his gun, and went back to the clinic to begin killing people.
That is a whole lot of guessing and supposition on very very little actual content.