At 11 a.m., a resident came to look for a colleague who lives in apartment 901 of building 4, Lansi Apartment, but failed to get an answer after knocking on the door and calling the mobile phone. Sensing something was wrong, the resident immediately called 110 to report the alarm. After the policemen rushed to the scene and pried open the door, they found that a family of three had been killed inside. One...