Zhang Heng was more familiar with the library than the dorm room he had lived in every day. He would either spend his time there or the gym during the extra 23 hours he had. Since a regular of the place, he made a copy of the door's key, usually entering through its employee-only entrance. He would first head to the basement to turn on the main power before entering the elevator and pressing the button to the seventh floor.
Unsure if the thing he was looking for in the library of even a living being, he quickly came across an idea. The library was located in the middle of the university, and since it went up to seven floors, it was perfect as an observation point for the entire area. From the top floor, there was a birds-eye view of the whole university campus. If the thing that entered the library was indeed a living being, it meant that whatever he did before entering was no longer a secret.