The Perfect Insider(すべてがFになる)

Due to Professor Kita’s suggestion, student Moe Nishinosono and Associate Professor Sohei Saikawa head to Professor Kita’s research institute. There, various experiments have been conducted in a low temperature research room. During the night a murder takes place. Two graduate students are found dead in the low temperature research room. How did the killer enter the closed research room and how did the killer leave the room?