If you'd like to know how to finish without the police suspecting you at all, leave the wallet where it is and implicate Sarah. Don't mop up the blood. Go to the table on the far right and get the key. Ask Sarah to leave and say that the cat is back. As soon as she's out of sight, drag the body in the back. Then grab the knife and put it with the other knives. Drag the body into the freezer. When the police ask why you asked Sarah to leave, say you didn't.
Perfectly in the clear uwu