If he truly has Schizophrenia then we have to go back to day one, and Ol Mom saying you have the right person, and hearing her clarification of what she ment by that statement. Now if this is true, be did not just get it is Colorado, this has been something his parents have delt with for a very long time IMHO. He didn't grow up uneventfully, earn a college degree or 2, and suddenly become Schizophrenic. Mom and Dad know a lot more than they are admitting to, and why they have an attorney now.
As far as the gun companies being responsible, the guns are reported to all be legal guns, 2 of them bought from the Bass Pro Shop store. There legal obligations I would think are iron clad legal, so you can not blame them. Not sure about other sales, but they better have all the paperwork 100% perfect. I'm sure they have grilled them totally already, and sure those salesman were sweating bullets about it. Can you imagine seeing the guys face in the news and know you made that sale?