Sam and dean have been using all their time to try to figure out how to defeat Amara and how to save cas, they got nothing. So they decided to do a case in a high school.

After spending a few days trying to figure out who and what was after the killings, they finally knew.. It was you, a high school student, a 15 year old kid!

they approached you in alleyway, you were the monster and was behind the killings, even though they knew you were the one behind it all they had no idea what you were

they have their guns pointed at you and you reached a dead end so there was nothing you could do

one of the men, the short one speaks, it was dean

"We know it was you, kid. What are you?"