Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

"Why did you give up?" Yang Sen handed over a water bottle, and Yang Lin took a sip and continued his analysis: "The pipeline entrance is 10 meters away from the water tank, and the interior is narrow, making it too difficult to move the body. In comparison, the fire escape is more convenient, and you can directly observe the water tank." He pointed to the scratches on the well wall, "The scratches here are shallower than those in the fire escape, which means that you only tried it once before giving up."

Near the community wall, Yang Lin discovered fresh climbing marks. Some of the spikes at the top of the wall were bent, with blue fibers hanging from them. "The suspect likely entered and exited the community from here," he said, measuring the wall's height. "It's 2.2 meters, not difficult to climb. There are size 44 shoe prints in the soil outside the wall, with a stride length of 80 centimeters, consistent with landing characteristics after climbing over." On the asphalt road outside the wall, there was a 10-meter-long tire track, 18 centimeters wide, indicating it was a motorcycle tire tread.

“They came by motorcycle,” Yang Sen said, taking a picture of the tire tracks. “Judging from the wear on the tire treads, the mileage is over 30,000 kilometers, so it’s probably an old vehicle. The red soil on the tires matches the soil in the community’s green belt, which further confirms the route in and out.” But the tire tracks disappeared at the intersection, becoming blurred by passing vehicles.

Back at the entrance of Unit 3, the two summarized their investigation results. Yang Lin drew a route map in his notebook: "The suspect rode a motorcycle over the wall, entered through the green belt to reach Unit 3, pried open the fire escape to enter, observed the location of the water tank, went out through the unit door to the water tank, returned through the fire escape after committing the crime, processed evidence in the basement and green belt, and finally climbed over the wall to leave."

“But the key tools and murder weapon have not yet been found,” Yang Sen said, counting the evidence bags. “There are only some fibers, cigarette butts, buttons, and blurry shoe prints. There is no physical evidence that can directly identify the suspect.” He looked through the investigation records. “There is no match in the fingerprint database, and DNA comparison will take time. At present, we can only determine that the suspect is 178-183 cm tall, wears size 44 shoes, smokes Yuxi cigarettes, and may be engaged in manual labor.”

Yang Lin pointed to the fingerprint photo on the water tank opening: "Although this unfamiliar fingerprint is clear, there is no prior criminal record for comparison. Blue polyester fibers are commonly found in work clothes, so it may be a decoration or maintenance worker, but we have checked all the decoration teams in the community recently, and none of them match the characteristics." He sighed, "These clues can construct a crime route and some characteristics, but they lack direct pointing, and we still have to wait for further test results from the technical department."

As the sun set, the two men finished their investigation. Yang Sen placed the last bag of evidence into a storage box, which contained 12 fiber samples, 3 cigarette butts, 2 buttons, 5 shoe print rubbings, and 3 bloodstain samples. "Although we didn't find any major direct clues, this indirect evidence can piece together the crime," he said, patting Yang Lin on the shoulder. "At least we know how the suspect entered and exited the premises and committed the crime, which narrows down the scope of our subsequent investigation."

Yang Lin gazed at the water tank gradually being enveloped by twilight, the afterglow of the investigation lights shimmering on the water's surface. "The body hasn't been retrieved from the water yet," he said softly. "Perhaps the key clues are on the body, but based on the current investigation, we've done all we can." In the distance, the sound of a technical department vehicle could be heard; they were packing up their equipment, preparing to take these clues back to the laboratory, awaiting scientific testing to uncover more secrets.

The residents outside the police cordon had dispersed, and the neighborhood had temporarily returned to calm. But everyone knew that once the secret in the water tank was revealed, this seemingly peaceful neighborhood would be thrown into even greater turmoil. Yang Lin and Yang Sen's investigation records filled four pages, with every analysis and deduction pointing to the murderer hiding in the shadows. Although there was no direct evidence yet, the outline of the truth was gradually becoming clear amidst the interweaving of numerous clues.

Meanwhile, the air conditioner in the community property management office hummed. As Wang Shuai plugged the surveillance hard drive into the host computer, the static on the screen gradually turned into a clear image. "We started checking on September 10th, focusing on the area around Building 3 and the entrances and exits of the perimeter wall," he pointed to the sixteen surveillance feeds on the split screen. "We'll fast-forward every hour, but we can't let any suspicious individuals slip by." Auxiliary police officer Xiao Zhang's freshly brewed strong tea steamed on the corner of the table, the aroma of tea mingling with the electronic smell of the surveillance equipment, filling the room.

The discovery was made within the first hour of reviewing the surveillance footage. At 3:17 PM on September 10th, a surveillance camera on the east side of Building 3 captured a middle-aged man in a black jacket, carrying a silver suitcase, loitering in the green belt near the water tank. "This man walks with a slight limp," Xiao Zhang paused the footage, highlighting the man's gait with a red box, "His left shoulder is lower than his right, and his left hand is always in his pocket, which matches Zhou Qiang's description of suspicious persons." The man stood under the ginkgo tree for about five minutes, occasionally looking up at the water tank, before dragging his suitcase towards the fire escape.

“Check this person’s entry and exit records,” Wang Shuai’s fingers tapped on the keyboard, pulling up the surveillance footage from the community gate. “She entered the community at 8:23 pm on September 9th, also carrying this suitcase. The registration information is ‘Visitor, looking for Ms. Zhang from Unit 2, Building 3’.” However, there was no record of Ms. Zhang visiting the property management’s visitor register on September 9th. The signature in the signature column was too illegible to read, and the contact number was not in service.

“There’s a problem,” Wang Shuai slammed the registration book on the table, the paper wrinkled from the dampness. “False registration, and he even deliberately appeared near the water tank. He’s definitely a suspect.” He asked Xiao Zhang to track the man’s movements. The surveillance footage showed that at 3:40 p.m. on September 10, the man entered Building 3 through the fire escape and came out empty-handed at 4:15 p.m. His suitcase was nowhere to be found. He then walked straight out of the community gate, his gait more hurried than when he came in.

The police officers investigating the migrant workers brought back new information. "Three renovation teams have been working in the neighborhood recently, but all have complete registration records," an officer said, flipping through his notebook. "None of the migrant workers were wearing black jackets or carrying silver suitcases, and the surrounding shops said they hadn't seen this person before." Wang Shuai suddenly remembered the motorcycle tire tracks outside the wall: "Could it be that migrant workers are riding motorcycles in and out, using visitor registration to cover their tracks?"

Upon reviewing the surveillance footage again, Xiao Zhang made a discovery in the underground parking garage. At 8:45 PM on September 9th, a man entered the underground garage carrying a suitcase and emerged empty-handed half an hour later. "The garage's surveillance cameras have blind spots," Xiao Zhang zoomed in on the footage. "He probably hid the suitcase somewhere in the garage and retrieved it on the afternoon of September 10th." Wang Shuai immediately led a team to investigate the underground garage. Behind the parking space corresponding to Building 3, they found fresh wiping marks and faint silver paint chips on the ground—the same color as the suitcase. (End of Chapter)