Daily Flash Fiction Challenge

BANG BANG BANG
The sounds clatter through the empty halls. It has been a week after the apocalypse started and there are a few lone survivors. David is with his family, hiding in the CDC in Atlanta. He has his dad and his little sister, Alex and Kenzie.
"David I'm scared!" Kenzie cried out. They only have each other. David wraps his arms around his sister, she was only 7. David was only 12.
"Just stay quiet." David whispered. The banging got closer to the small room.
BANG
"David!" She yells.
"Kenzie. Be quiet." David says through gritted teeth.
"There's something out there." Kenzie whispers. David nods and starts to usher her towards the vent in the wall. He quickly unscrews all the bolts and helps her in then closes it.
"Be safe." David asks.
"Where are you going?"
"To fight."
"Fight who?"
"The zombies." With that, David walks away, grabbing an axe and getting ready to unlock the door. He opens it, immediately nailing a zombie in the top of the head. Kenzie watches with terror. One by one David kills the zombies, fighting them for what he has left. Until Alex limps towards him. He was no longer their father, he was part of the walking dead. David wants to fight him off, it appears he is the last one in the building but he can't bring himself to swing that axe. Kenzie cries silent tears as she watches her dad rip into her brothers neck with his teeth. They fall to the ground, David not able to do anything except wait to die, and Alex digging in. Kenzie just watched everything she had left be destroyed. She grabbed the wrench and hit it over her head, everything going away. She did it again, finally losing consciousness.