Guessing

"Interesting." Holmes closed the notebook in his hand. "It appears Mark Cohen had indeed come into conflict with those prostitutes. So, he led himself to the role of Jack the Ripper, all for the sake of seeking pleasure. However, he didn't expect that the deeper he got into the role, the more he lost parts of himself."

"These things were clearly recorded in his notes. He began to imagine that he was the murderer after the first killing was reported. By the time he saw the letter in the newspaper, his soul and mind had completely been devoured by Jack the Ripper, and in the end, he couldn't even tell who he was anymore."