Speculation:
Any kind of lab work would be done in a lab van. MOO
Perhaps LE received new tips or, more likely, analyses have come back on seized electronics, perhaps with stills or videos that originated from within the home, maybe revealing a subterranean chamber. Soundproof, a room survivors never saw but the victims might have. He lived there a loooooooog-island loooooooong time, didn't move up and out like so many people do once their careers take off. What wed him to it? Family history? Personal history? Did he have it just how he liked? When the family was away, did he perfect a secret room? Torture chamber. He neglected every other aspect of that home. And arguably, the family within. Is it because it had a bunker? His private sick retreat.
If only those walls could talk.
Maybe today they are.
JMO