The refrigerator
Spoiler ahead
At one point Reznik sees his flat owner, Mrs. Shrike, talking to police in front of the building, obviously about him - the cops are after him at that moment. Later on he gets back in the flat and finds it just the way he left it - with the fridge closed, and blood leaking from it. It doesn't make sense that police did'n't search his home. They would've found the fridge and wouldn't have leave it that way for sure. And Mrs. Shrike already had problems with that leak and certainly turned their attention to it.