The one concrete benefit of officially committing him would be that he could be prohibited from buying a gun from any federally licensed retailer. Of course, this would do nothing about any guns and ammunition he may already have amassed. Nor would it deter him from getting guns from private-party sales, which are exempt from background checks in many states.
I ended up admitting this patient, and he was released by the hearing officer two days later. He never took any medication, never reached the threshold for a federal firearm prohibition and left the hospital in the same state he arrived in. Like so many of his peers, he will not seek out therapy for the longstanding personality traits that seem to predispose him to violence and rage, and there is no way to impose treatment upon him.
The reason the mental health system fails to prevent mass shootings is that mental illness is rarely the cause of such violence. Even if all potential mass shooters did get psychiatric care, there is no reliable cure for angry young men who harbor violent fantasies. And the laws intended to stop the mentally ill from buying guns are too narrow and easily sidestepped; people like Nikolas Cruz and my patient are unlikely to qualify.