Confession

Mr. Chen fell to his death from a building after getting drunk. However, after reviewing the elevator surveillance footage, the police suspected foul play. Here are the statements from several suspects, all of whom had a motive to kill Mr. Chen. Please determine the true culprit. Mr. Wang from the 27th floor: I was drinking with Mr. Chen that night. After taking him home, we chatted for a while, and then I went home. John from the 28th floor: I just returned from a business trip tonight. I haven't left my home since I got back. Ms. Li from the 30th floor: We talk every night. Tonight, his signal was bad, so he went to the balcony. After chatting for a bit, he asked me to come find him. When I refused, he fell silent. I heard him slam the phone down, so I had to go find him. The elevator showed it was under maintenance, so I took the stairs. I knocked on his door, but he didn't answer. It seemed he was angry with me, so I had to go home. Property Manager: I'm on the night shift today. I was patrolling the building as usual. When I reached the 4th floor, the elevator was broken, but I had just checked it. After I repaired the elevator, I heard someone shouting 'Someone died!' from two different locations where objects had fallen. Investigation revealed: There were four different footprints near Mr. Chen's door within 12 hours. Along with Mr. Chen's fall, the balcony safety railing was also missing. Ms. Li frequently visited Mr. Chen's home. There was no surveillance in the fire escape. Elevator surveillance: 18:00 Mr. Chen went to the 30th floor, then left the building with Mr. Wang. 18:30 The elevator showed it was under maintenance, but no one was inside. 18:45 The property manager retrieved his toolbox to repair the elevator. 22:00 Mr. Chen and Mr. Wang came from the 1st floor to the 29th floor. Mr. Wang had something clutched in his hand. Mr. Wang returned from the 29th floor to the 27th floor. There seemed to be a sharp object in his pocket. 22:20: John came from the 1st floor to the 28th floor, carrying a suitcase. 22:25 The elevator showed it was under maintenance, but no one was inside. 22:40 The property manager retrieved his toolbox to repair the elevator. 22:45: The manager seemed to hear something and rushed out of the elevator. 22:50: Ms. Li returned from the 29th floor to the 30th floor.