From what I gathered, the perp was a convicted felon just released last year from prison. How did he get a gun?
The son (ex-husband) and his mother had kidnapped the three girls while they were in joint custody with the wife and took them to Central America. He had also taken out a fraudulent home equity loan just prior to that. He was captured, the girls were returned to their mother and he went to jail. He was released in September.
He (son) owed back child support - that is what the hearing was about yesterday.
His father did the shooting.
Undeclared possession prior to imprisonment, or private source after, like anywhere else in the US. I suppose.
I have to say that in Delaware, private sales do not require a background check, nor are they recorded. I am not sure what the burden of the seller is. I'll check the state code on this. But, of course, a felon here as anywhere is a person prohibited from even touching guns or ammunition whatsoever. FWIW.
Concealed carry is by application to and approval by Superior Court with background check, references by five registered clean adult voters, and a prescribed course of instruction, and advertisement to the general public.
Obviously, the perpetrator must have carried the gun concealed up to the point of use. And also, unsaid but obvious, any law-abiding citizen intending to enter that building must be metal-free -- not even a pocket knife or pointed instrument other than a writing utensil.
So the general areas about the entrances to the building are inherently target-enriched zones. My guess is that this is probably the only location where the perpetrator would have found his ex-wife unweaponized and able to be approached by him. Apparently he had no workable exit strategy. However, it is clear that he could not have been intending a rampage on others.