From the fact that the girl did not launch an attack immediately, it seemed that his statement had some effect. Gongsun Ce recalled the scene of their first meeting, becoming more confident in his assessment.
"The scars on the wreckage were like those torn by wild beasts, quite different from your incredible technique. There's not a drop of blood on you or your knife, too clean for a murderer. Your first reaction when you saw me was to knock me out, not to kill, something a murderer wouldn't normally do." Gongsun Ce analyzed each point, "Most importantly, had you been there earlier, the wreckage couldn't have remained intact— you know what I mean. Your superpower would have warped everything."
If the girl had reached the alley and started the massacre earlier, the chunks of flesh and blood Gongsun Ce saw would have been distorted by her power, not maintaining their basic shapes as they now were.
Considering her newbie status, piecing the whole process together became quite simple.