The haunted house

The house reeked of mould when I set foot on the sagged concrete floor. My boots screeched as I stumbled over a dried pumpkin that appeared to have been hardened over some time. As I crouched down to peer onto it, I broke into fits. My asthma was getting over me again. My eyes started to water.
Through the mist, I could see a parchment that had been written in ink that was still intact. Curiosity got better over me and I bent to pick it up. My lungs, by now, was heaving heavily and squeezing sounds were heard from my lungs. I just had to get away from all of it. I grabbed the parched paper and made my way towards the patio. Just then, I heard a bang. The large metallic door has been closed before my very own eyes probably by gusts of wind. Weepings were resonnating near the pumpkin but I could not gauge where it emanated as it was deafening.
I felt trapped by my own curiosity. I retrieved the missive that I had put on my pocket and pored over the small scribblings .The language was concise and clear to understand though.
It says:
Dear Reader
By the time, you read the letter, I will be dead. I murdered my own sister long time ago. The pumpkin attested to this fact. Too many people have ignored that witches uses real pumpkins to do their evil deeds and yet Halloween is considered just a festival. They are just mocking but they have not seen the extent that evil has reached everywhere. Satan is everywhere. Beware. I was possessed, unbeknownst to me when I killed my own sibling. Yet I felt glee at that time. To you, who is reading this letter, do not fret, for you are mine now Ha ha ha!
Yours forever
Stanley.

Stack of biles were rising up my throat. I spat on the floor. My legs were crumbling on the floor. I heard a loud cackle. Then that was all. Blackness engulfed me and I stumbled on the floor with a loud thump.
My head was reeling. Light shot through my eyes as i made an effort to open my eyes, that sent me blinking hard. After some time, my eyes adjusted and I could see forms around me. A huge pumpkin, cracked floor. My mind could not recall anything.
Then I saw a large mirror next to the latched door. Groping, I stood up, feeling sore in every muscle in my body.
I looked into the mirror and screamed.
My eyes were puffed upbut it was the face that I could not recognize. Something was not normal. My hands were trembling and what I saw next was someone I know. Tapping me on the shoulder, he veered towards me, grinning and just gave me the thumbs up. "Thanks for freeing me. My name is Stanley."