Could you explain 1439? I'm not sure I un…

Could you explain 1439? I'm not sure I understand the ending

http://fifteenhours-creepystories.tumblr.com/post/172386063691/creepypasta-1439-the-watcher

SPOILER ALERT

Two possible meanings to the story – 1, the author is suffering from PTSD and the weird horns and claws that he sees on the others are merely hallucinations. Or 2, the author is actually seeing monsters for reals.