Mental health institutions were shut down because of the widespread neglect, abuse, and sexual assault that happened there. Not to mention the lack of funding. Did Regan pass some bill sent by the legislature? Yeah sure, but he wasn’t raping special needs women with impunity. People were also (rarely) involuntarily committed to get rid of them. The whole system was fucked and has been absorbed into prisons now. I don’t have any feelings for Regan one way or the other (way before my time tbh) but pinning that on him or conservatives isn’t really correct.
I’m not taking a stance on that at all, I’m just stating Regan didn’t shut down mental asylums that used to contain all the school shooters.