chinchillas

I have a question about chinchillas. I gave my chins away about a year ago. My friend called me yesterday and said, one of the chins gave birth and ate the young kit. This beautiful chin had never did this before. She gave me two litters and this girl one healthy kit previously. She was bred to the same male. The only difference was this time her previous kit(male) was still weaning last December when she conceived. This baby was 3 and one half months old. My books say the male is not sexually mature until they reach 6 months old. Could this have been the weaning male's kit? Would the mother of killed it or do you think it was still born? Or am I barking up the wrong tree? I love these little guys and I am sick about this. Anybody and suggestions?:(