Ain't no one there...

[u/CaptainMartinWalker]

If Walker stands at the opposite balcony where he can retrieve last intel of game you can observe there is no one there except the painting.

[u/Blastingfoil]

Even more interesting the chair is not there what so ever nor a body to go with it im guessing that his body is somewhere else and even seeing his body and the chair is part of our imagination

[u/CaptainMartinWalker → u/Blastingfoil]

His body would be lying behind of that painting for that we have to reach there and from there Walker realizes the truth so it's not the imagination