At 11 a.m., a citizen came to find his colleague who lived in apartment 901 of building 4, Languan Apartment, but he couldn't open the door. When he called the mobile phone, no one answered it. Feeling that something was wrong, the citizen immediately dialed 110 to report the alarm. After the policemen rushed to the scene and broke into the house, they found that a family of three had been killed at home...