The Sinister … Who or What?

The grinning face stared at Andy from the darkness beyond his bedroom window. He lives on the 14th floor …

“Is it real? How is it possible? What is happening? ” He questioned himself. He tried to ignore, turning to the opposite side. He sighed and he had shut his eyes tightly. After a while, he took a glance at his room. When he looked towards the window, sweat ran between his shoulder blades … Impulsively his eyes shut. He slept. 

The morning sun rose bright with red rays, which made Andy recall last night. He was floating in his dreamy world on his bed, Until lighting shot and in fraction of seconds he was on his drawing table.There were different colours and a big sheet lying on the table. He drew what he saw with his will.

Big, yellow eyes; Dark shadows under the sunken eyes; Rubbery, red lips; Hardened features; Immobile face; Glowing, green skin; Long, white fangs and a malicious grin. This is what he portrayed. 

Few hours passed, he googled at the sketch without even a blink. He gazed at the page in astonishment. As he thought deeper, he realised that he had seen the face earlier, other than last night. “Oof … Let me just leave this. ” He talked to himself. He took a rest and swam towards his rest room.

He noiselessly pulled the door and went to look into the mirror …

He saw the same face. “OH! ” was the sound that echoed. “ Was that my reflection in the bedroom window ?” He wondered. He confessed in affirmation, “ YES.”   

So readers; THE SINISTER… Who or What? Who was horrifying or What was horrifying? Andy or The Window? What could have happened?