The text message that shouldn't exist

At exactly 3:17 AM, I received a message from my best friend.
The only problem… he died three days ago.
The message said: “Don’t come to school tomorrow… something is waiting for you.”
I thought someone was playing a sick joke. But when I got to school the next morning, everyone suddenly went quiet and stared at me.
Then my teacher told me something terrifying: the police had found my friend’s phone in his room the night before… untouched.
And right then, another message appeared on my phone.
“I warned you… it’s standing right behind you.”
Would you turn around?