I agree that the guy knew that the doorbell camera was active due to the light. But I don't think NG would've opened the door to him or to anyone she couldn't see, especially at that time of night. I think the flowers were a crude attempt to shield his face from the camera while he was disabling it. After dealing with the camera, I'm guessing that he either picked the lock, waited for an accomplice who was already in there to let him in, or maybe went around the back to break in.Ah, that makes a lot of sense. Perp has info that the camera is inactive, but sees the light and gets worried that it's still on. Wants to knock on door, but camera will let NG see him and ruin his ambush. Improvises with flowers to temporary block camera so NG can't see him; NG opens the door blind to the danger.
JMO