Yes, they (or rather, Eben) did.

This is a common problem with book to film adaptations; always bits and pieces of information left out, leaving viewers slightly confused.

Anyway, back to your question. According to the comic(s), there were around 462 people in Barrow just before the attack, and 19 after. The survivors hid in an abandoned industrial furnace (basement-like) and Eben went out for food whenever possible.