This sounds a whole lot like a drug dealers’ version of the cops’ wrong-address no-knock raid. I can see killing the older kids; they could testify. But a baby?
But the cops don’t sound any more rational. Granted, anyone who would name her child “Four” is probably none too stable, but I think that any of us, on learning that our kid had been offed for no discernable reason, would get pretty wild. So them big brave men in blue can’t deal with a grieving woman without using a Taser?