Interpol Wang returned to the Bureau after investigating a murder scene  The guard Lao Zhang asked him what the result was  Wang said he knew that the murderer had been to the scene  Lao Zhang knew that Interpol Wang was teasing him, because he didn't need Wang to tell him at all
He knew that if someone was a murderer, he must be at the scene at the time of the crime
If Wang Wu was not at the scene of the crime, he would not be a murderer.