This was of course good news, and they were certain that the shoe prints showed no signs of being disguised with other shoe sizes. Combined with comparing the surveillance footage to Dao Zhiyong's gait, we all concluded that the murderer was not Dao Zhiyong.
Though the two looked exactly alike, their gaits were completely different.
Dao Zhiyong’s left foot tended to lag slightly, by about 0.5 centimeters, while the murderer strode forward with an unhesitating gait.
Don’t underestimate the importance of observing gait. Although there is no scientific basis for this for now, experienced old detectives can easily analyze whether multiple people are the same person based on their gaits. It’s like if you go to certain places and see large signal communication devices, you can be ninety-nine percent sure it’s a criminal investigation team.
With so much evidence, and Dao Zhiyong having no motive for murder, he was quickly released. However, he still had to rest at home recently and could not participate in this case.
Su Yaxin temporarily took over his work in the document examination room. This day, we received another update from Cao Xiangyang, saying that a patrolling police officer had been brutally murdered. He was from Ma Ting's department. At the time, I wondered, was this guy seeking revenge against Ma Ting and his men?
While reviewing the surveillance footage at the traffic management office, I noticed that the person looked very similar to Cao Xiangyang's gait. No one else could tell, but I had seen some of his previous videos, and I was certain, even if others didn't believe me, that the person who killed the patrol officer was Cao Xiangyang. I had originally thought he would find some accomplices, but he dared to act alone.
While examining the deceased patrol officer, I discovered wounds similar to those on Ma Ting's body. As expected, it was the same perpetrator. He was shot in the same way, shot from the left side, and the shell casing was found nearby. After prior comparison, it was found to be the same type of bullet. The firearm was even a Qsz92-9g automatic pistol, a standard issue for criminal investigators, equipment used by anti-drug and SWAT units.
The earliest 9mm police revolver, put into service in 2006, was soon praised by police officers for its low recoil, accuracy, and excellent rate of fire, making it the undisputed "Number One Chinese Police Gun."
You should all remember this. While we were studying it, the body was taken away, which was infuriating. This guy really had to target the police every time, and now another one was dead. However, during the autopsy, another astonishing secret was discovered: a piece of paper was found in the deceased officer's head. After unfolding it and using a sodium hydroxide reagent, we were able to see the writing on it.
Su Yaxin helped us discover this because she observed that there were traces of phenolphthalein solution on the paper.
"The text on it will slowly appear with my methods. Just you wait!" In the document examination room, Su Yaxin said. She had already added the sodium hydroxide. At that moment, Xia Xiaoling, Liu Yuning, and I were eagerly watching. Beside her was another piece of paper, found in Ma Ting's head. It turned out these pieces of paper had been in their heads all along, and we only discovered them later. As for how they remained there, we suspected that the bullet released them as it passed through the victim’s head. The specific principle should be related to physics. Although this is somewhat difficult, anyone with a basic understanding of firearms and physics could achieve it.
Only when Su Yaxin saw the words did we realize they read: "It's not over yet. We will continue to play different roles..."
These few words felt like receiving a death notice. Did they intend to continue killing police officers in this manner?
But we had no idea when they would strike again. Seeing this message, everyone fell into a panic, fearing they would become the killer's next target.
However, Liu Yuning's reaction was one of anger: "This scoundrel dares to target our police force! Quickly investigate Xiao Huang's (the previously murdered police officer) case, cross-reference it with Ma Ting's case, and thoroughly investigate for any connections!"
"Captain Liu, we are already investigating. All departments at the provincial level are extremely busy, as it is now our own people who are being endangered. Who isn't nervous!" One detective’s response, instead of easing the situation, only drew Liu Yuning's reprimand. At this point, anyone who crossed her was likely to face the same fate. I tried to stay away and search for answers myself. I didn't follow the autopsy in detail because Xie Chuchu was there, and the body was likely similar to Ma Ting's. My task mainly focused on the surveillance footage before and after Xiao Huang's incident.
Later, I learned that Ma Biao possessed a unique skill in image reconnaissance. When he was in the Information Technology department, he told us, "Watching surveillance footage is one thing, but how you watch it makes all the difference in the information you obtain. Image reconnaissance is when you have video and photos related to a case for the personnel to analyze, allowing them to find many useful clues."
Initially, Ma Biao just said this, and of course, not many people believed him. But after persistent effort, he seemed to have found something overnight. He Xin and Yuan Hezhu were both watching him screen the footage.
"What kind of technique is this? I've never seen it before," He Xin asked. Ma Biao, however, didn't seem surprised. Perhaps his technique was learned in China, as He Xin's expertise was primarily Western.
"This is our image reconnaissance team's expanded range targeted search method. After last night's screening, I discovered a male carrying a shoulder bag appearing within the activity range of Xiao Huang and other patrol officers. Look at these few streets. If you search these designated areas, you will definitely find some clues. Human dander and hair are constantly shed."
"Indeed, but these images are a bit blurry. How did you make them so clear? Did you use a 'clarity enhancement' technique?"
Yuan Hezhu’s question was well-intentioned, but Ma Biao explained, "Actually, achieving clarity in real-world images is very difficult. At most, we can enlarge the image and remove some impurities..." As Ma Biao spoke, his fingers didn't stop tapping on the keyboard. Soon, the image before us enlarged, sharpened, and had its colors removed, revealing a blue shoulder bag!
"Is that for women?" He Xin asked curiously.
"I said it was a male earlier. Look at his build and behavior; he's male. A woman wouldn't make such a vulgar pose, squatting against a wall to peek. He did this on every street. Actually, I didn't notice him at first. The blue shoulder bag caught my attention..."