Well... Teal can't be a killer cause he just arrived. And Tan is holding him. So both of them aren't suspects.
Since Rainbow says that she heard a girl scream, and she's cooking in the dark. She can't she anything... Unless... She can light up the Stoves. Ok.
So... The killer is chasing the victim for it then he brings bat after she get into kitchen she's stuck. And the killer decided to use bat to break her leg. Then, he hide it in the box when the victim decapitated he would have to use Cleaver to cut her head... And hide it in the closets... But let me guess... The killer is...