I specifically said I was talking about the mentally ill shooters, who do currently buy their weapons legally. My comment excluded criminals, who we know get guns from the black market already.
There is a wide spectrum "mental illnesses." What laws specify the specific mental illnesses, which disqualify gun ownership?
Some claim we are in the midst of a "mental health crisis." (My opinion is, much of it stems from dangerous drugs, like speed, opioids, etc.)
ADHD, Bipolar, Unipolar, Schizoid, etc? We are all just babbling.
I have several relatives that take depression meds. One threatened suicide, 40 years ago to start her life cycle. In her case, the meds keep here fairly normal, although she says at times, it is very uncomfortable for her. I seriously doubt she would ever be a danger to others.