The Dead Inside 2013 one on netflix

A bad night out just got a fair bit worse, it’s the end of the world! Something terrible has happened, the undead are out in force; roaming the streets and devouring all who get in their way. A group of soldiers, civilians and teenagers take shelter in a local school for protection from the undead hordes outside, but no rescue is coming. Food is running low – morale doubly so, tensions are high and things are looking bad when a stranger arrives outside the gate. Then they get a whole lot worse.