Marco was in his office the whole time that the whole world was panicking. During those times, he don't know what is happening with the world outside his office. Soon the zombies found him and that was the time that Marco realized what was happening outside his office. You would start with a machete on hand, but do not worry as soon there would be some guns falling at the attic. Each zombie you kill would earn you money. You can use the money to upgrade your character. The game becomes harder and harder as you make some progress, so you need to upgrade your character.