"Well, you know, she was just another law-abiding gun owner. Until she wasn't."
I guess gun stores should start hiring psychics who can use their crystal balls and deny sales to anyone who will commit a crime in the future.  Yes?

"Congress voted to OK mentally ill people owning guns." 
When did they do that?  According the ATF, people who have been adjudicated as mentally defective are still prohibited from firearm possession.