Head downstairs to the lobby

You take the staircase downstairs, avoiding a few old bloodstains and a half rotten corpse on the way down. The lobby is where everyone in the building got their mail. Everyone got a box on the wall, except for apartment No.19 for some reason, which the numbering skips. Must've been some labeling error from way back when the mailboxes were set up.

There's a few ways you can go from here. There are stairs leading to the underground basement and parking garage next to you. The exit to the building is through the thick glass doors in front of you. The door to the security office is by the exit. There is also a corridor leading to the ground floor flats, but you see a few infected milling about from around the corner. You'd best avoid that area.