Kyle has actually seen his own evil twin before, so yes, he's pretty goddamn sure he knows what's going to happen if he goes through that mirror. And he certainly can't let that little girl get hauled into some carnival purgatory either.

So Kyle knees his other self in the groin.

It works to get the doppelganger to lose his grip. Kyle squirms away and sprints to Molly. Before he can think to do differently, he steps on the little mirror-girl's wrist to make her let go of the real Molly. He doesn't feel good about it, but he does it anyway. He's tackled by his own mirror image a moment later. He hits the ground and feels his chin bang against the floor, biting the tip of his tongue hard enough that he tastes blood.

He squirms, trying to get onto his back but he feels his doppelganger get an arm around his throat and press, cutting off his air.