Lea comes from the coffee shop(this meeting was about her large debt to him) she got angry and tried to kill the victim, pushed him, he then lands on the dumbbell. She flees and leaves the door open.Jii shows up, It was chilly so Jii bumped the heat, saw the victim dead, finds evidence and covers up Lea by picking it up, he find the victim is still alive and stands up, Jii hits him on the head with the dumbbell, leaves and closes the door. Max comes and see's Jii leave,goes in and see's the Victim, noticed the house was warm, and leaves with the door unlocked fearing the worse (after maybe seeing a dying message, he also removed to protect a friend). This is why he was vague to the police, Jii covered for lea and ended up killing him, and lea created an Alibi thinking she murdered the victim. There was no fingerprints or hair because everyone wore gloves and hats because it was cold. The murderer was Jii(once again)! cased closed