you were with your friends, having lunch in the cafeteria when you heard people screaming and running in, scared of something... when u got up and tried to look.. you saw it.. a hoard of zombies attacking which prompted you to run
you tried to save as many of ur friends as u could, but in the end, you and Riki, the popular guy of the school who was known for being cold, straight-forward and closed off, were locked up in a classroom to keep yourself safe. The other survivors were probably scattered across the school in different rooms, yours friends all dead, their blood still on your clothes
"Everybody is dead.. i think its just us in this school.." he mumbled, leaning against the furniture which was place against the locked door for support. The classroom was connected to a storeroom which contained all snacks and water confiscated from students