I saw in the Columbus Dispatch where the mother of the OSU attacker is suffering from a similar syndrome as the Boston bomber mother: refusal to believe her son was capable of the acts attributed.
It's interesting that happened in two mothers of Muslim migrants. Very anecdotal of course and I'm not sure how often this occurs in non-Muslim mothers of sons who do heinous acts but there are at least a few explanations:
1. Strong desire to not believe bad things about your kid, thus you protect yourself with denial.
2. The apple didn't fall far from the tree - that is, the tendency to disbelieve reality was how their sons were raised thus making them capable of heinous acts on the basis of delusions.
3. Muslim migrants feel, in general, so disconnected from the culture that they have zero confidence in institutions like the police, media, government, etc, despite receiving the assistance that sprung them from hellholes like Somalia.
I hope the explanation is the first one.