No, there was absolutely no way to know or predict. He had a totally clean record (except for a minor misdemeanor that was essentially equivalent to getting a driving ticket).
He was a little weird, but if you tried to throw out of society (not that you could even if you tried) all people who are slow, you’d have so many people to start with you’d never get anywhere.
Also, the DA yesterday confirmed that the Medical Examiner determined their was no sexual abuse in this case. Nor did Aron have any history of such abuse in the past.