The Killer Upstairs

I received a police alert: a murderer is on the loose. Someone knocked on my door, claiming to be from Property Management—but our complex has no property management. I played dead. The couple upstairs was having a fight, so I sent a message to the Residents' Group Chat. The other person sent a photo: a woman cut in half. 'Sorry for the noise, I've already taken care of her.' The killer lives right upstairs from me.