Possible, but how did the woman get into the house? How is it that the stepdad was there just 15 minutes before these people were there? Did they have something against him? Is that why the mom moved into a different apartment, because stepdad had something going on, and threats? Drug money owed? Deals not completed? She tried to distance herself, they following him there to find out a way they could show him they meant business thinking he'd be effected by the boy's disappearance? There are still a LOT of possibilities, too many to even grasp really.
Sounds like they're getting to the bottom of it at least. At least, let's hope they get ALL the parties involved.