At 11 o'clock in the morning, a citizen came to look for his/her colleague who lived in apartment 901 of building 4, Lushan Apartments, but no one answered the door, and when he/she called the mobile phone, no one answered it either. Feeling that something was wrong, the citizen immediately called 110 to report the emergency. After the policemen rushed to the scene and broke open the door, they found that a family of three had been murdered in the room...