Someone had once suspected that the robberies were the work of a group.
Zheng Tan was no Sherlock Holmes, but he knew it was more likely that committing a burglary in the residential quarters required at least someone on the outside as a lookout.
However, the police that came to investigate didn't find anything, so the matter was put to rest. During that time, all the residents who rented their place out had to come back to explain their situation to the resident committee. Eventually, they all signed an agreement to promise to ensure the trustworthiness of their tenant.
Zheng Tan heard a "clang". It came from the security door out front.
These two thieves had access cards and were very familiar with the building. Their target should not be the few retired faculty members.