Captain Vivi said: The murderer came to this room after Bing Bing died. It can be inferred that the biggest suspect is her son, the only person among her children. Reason: My son found the body after work, so Grandma Bingbing didn't die at work. To sum up, my son came to this room before and after grandma Bing Bing died. If Captain Meow is right, then my son is the murderer.