I mean, provided the crime scene didn't literally spill outside of the victims' rooms, they could've just gotten up and walked right out and went to work/school without even paying attention.

I live with 3 other guys, 2 of them work much later than me, so I've never seen them once in the morning and I just get up and walk straight out the door to work. Some days we just go straight to our rooms and I'll go many days without even seeing them.

If I came home late, or was passed out drunk when a crime happened, 2 of my roommates could literally be dead in their rooms for probably 5 days before I even questioned anything. Their windows are on a side of the house I never see, so they could've been broken.

It's obviously an extreme circumstance but it's very possible.