The Silence Woke Her

The sound of silence woke her. She groaned and rolled over to look at her alarm clock. “3:00 am” it read in bright red lights.
“Silence, go back to sleep,” she muttered at the pup. The young dog simply sat on the bed, whining the most pitiful whine he could emit.
She huffed and reluctantly got out of bed to let the dog out into the backyard. Anything to get him to sleep again, so she could be rested for her 6 am shift. She yawned as she watched the pup happily prance out the door and into the dark of night.
A few minutes later, Silence scratched at the door, wanting in so that he could return to sleep in his master’s cozy bed.
Once she left him in, she led him upstairs, curled up back in bed, and fell asleep yet again.
The following morning, she woke up to find her companion no longer in the room. She thought it odd, since he usually waited for her. She decided that maybe he had already gone downstairs and was waiting for breakfast. But wait. Hadn’t she closed the bedroom door again when they returned from their 3 am trip downstairs?
She looked around downstairs and saw no sign of the pup. He was nowhere to be seen. Eventually she thought she may have not let him in. She walked to the back door and pulled it open, and was greeted with a horrific sight. Her sweet little pup was strung up in a tree, blood and guts splattered on the ground below him.
She let out a blood curdling scream, but a thought suddenly hit her. If her pup was dead, what had she let in?