The Masked Killer

Everything happened too quickly. One moment you're being held hostage in your school.
Then suddenly all of the captors get murdered.

The next moment, you're at the police station, being interrogated. You see the murderer's mask on a picture. A black and red Guy Fawkes Mask.

But there's something nobody else knows except you.
He wore the same uniform as you.
He goes to the same school as you.
And not just that, but he knows who you are, too.