http://www.wmur.com/news/baby-doe-identified-1-in-custody-wcvb-reports/35348916 She (the mother) tried to be responsible, but she was on drugs," said Yessiomora Torres (a neighbor). "She talked slurred, she’d come out and smoke a cigarette, her daughter would be crying."
....
Torres said that when she stopped seeing Bella that she assumed the girl had been taken by the Department of Children and Families.
This is perfectly possible. Except that either the mother or her boyfriend knows how the child came to be dead and in a trash bag. And I'll bet whichever one it was shared that information with the other one.
I'm guessing that with the drug involvement these are not so much evil people as they are pathetic. But go ahead and get your pitchforks and torches and ropes out - it's what good folks do.
stay safe.