Why did Rem kill Lai Yueang?

The man went to the villa for the first time and asked for a job, which was very serious. At this time, Rem's doubts about him gradually disappeared. A few hours before reading the document, he and Rem went shopping. Rem smiled back at him, but he was bitten by a dog and died under a curse. The man read the file and knew everything about the villa, saying that he would eat and drink in the villa. Rem must feel strange (Rem suspected that he was a spy sent by the enemy) and then killed him.