The killer say there is 2 dead body and will show the police if they comply to his rule. The 2 dead body is Tracy and the baby ... But the movie biggest weak point is the killer have already started the plan more than 1 year ago but during that time, Brad Pitt is not in town yet. Or in another word, the 2 sin have not being fix yet. As per the old detective say, the killer is a perfectionist. The 7 sin must be present and only will he start the plan. If not, he could have already escape once the police find he's home. Btw, that also another weak point ... The killer could have pretend he didn't get some grocery or something and calmly turn and walk down the stair. He did not need to shoot them. Because, although they found he's place, he could still be able to carry on the plan and even have already carry out the plan ... as per what he have done to the drug dealer ... The city is big and he is using cash and cover he's trail, so don't think the police can find him within 2 day which the killer will have completed the plan. Anyway, this was my thought when I initially watch the movie 20 plus year ago ...