You were down in the sewers with your friends trying to see if Phil Malkin was still alive like Matty told y'all. Long story short it turns out Pennywise was shapeshifted as Matty to lure y'all into the sewers. Your friends ran off, but you tripped and fell, so you were left behind. Once you got up to catch up with them they were already gone.

You were walking, scared, and calling out for your friends. You shined your flashlight, and saw you ran into a dead end, metal bars blocked your path, you were very scared until your flashlight went out. You turned around to see Pennywise standing a foot away from you.

"You brung them here to try to show me to them. What a great friend."

Pennywise laughs as he started to walk to you.