Police believe Thaina da Silva Pinto, 21, and husband Fabio Luiz Lima abducted 22-year-old Rayanni Christini Costa and planned to remove her baby with a knife to keep for themselves.
But the infant and mum both died as the couple cut through the woman's belly, according to police.
The chilling moment the mum-to-be first met her alleged killer before being lured to her death was captured on CCTV .
