“The evil cop” face is gradually revealed.

Police collected 300 boxes of evidence, including a large amount of documents, and summoned hundreds of people involved in the trial. Cao's true face, known as the "evil cop", is gradually revealed.

The gunman’s identity and subsequent investigation were shocking. The killer was a policeman named Tsui Po-ko. The weapon was a revolver belonging to police officer Leung Shing-yan, which was stolen in the 2001 attack that killed An.

An, 24, was ordered to inspect an apartment complaining of noise in the Shek Wai Kok building at 12:05 a.m. on March 14, 2001. Grace was alone because his teammates were eating lunch.

At 12:25 a.m., An radioed the unit, announcing that he had arrived at the apartment, but no one responded to a knock on the door.

Shortly thereafter, the police station received another call, saying that gunshots were heard and that there was an officer lying unconscious in the building.

Upon arriving at the scene, the police found An dead, shot 5 times at close range. A pistol full of ammunition and a fast loading device with 6 rounds of An disappeared.

Noise complaints may just be fake because of being called from junk sims. Police suspect someone deliberately lured them in to steal a gun.

Armed police teams cordoned off the building and searched it. About 3,000 people, including 2,000 police officers, were questioned but no culprits were found.

After discovering that An’s gun was in Cao’s hands, forensic tests also showed that the DNA on the mask found at the crime scene matched Cao’s.

Cao went undetected in 2001 because people who had never been convicted would not have DNA records in Hong Kong’s justice system.

Investigating further, the police found Cao also committed a bank robbery on 5/12/2001.

The forensic ballistics expert determined that the gun he stole from police An was also used in the robbery.

At 12:10 a.m. on December 5, 2001, Cao, wearing a mask, stormed the Hang Seng bank branch in Tsuen Wan.

The 31-year-old security guard struggled with Cao, dying after being shot three times.

Cao ran away from the bank with HKD 490,000 and $1,000 in cash. Police tracked him into the Belvedere Garden shopping area but escaped through another exit.

From the descriptions of several witnesses who saw the robber remove his mask, the police painted a portrait of the suspect as a short-haired man, about 1.8 meters tall, offering a reward of HKD two million to the informant who helped with the arrest.

Police noted that the robber’s weapon appeared to be a police revolver.

After Cao’s death, police found he matched the description of the suspect according to images captured by surveillance cameras.

Important evidence is the red shirt, Mizuno shoes and left-handed characteristics.

The red shirt had the same logo as the one the robber wore found at Cao’s house after his death.

The shirt bearing the symbol of the Yinchuan International Motorcycle Tourism Festival was a gift given to Cao by the club secretary when he attended the exhibition in 2000.

Cao was also identified near the scene. He boarded a bus from Tung Chung at 11:11 a.m. on his wife’s card, then boarded a minibus to Tsuen Wan at 11:53 a.m.

Police discovered that after the bank robbery, there was an unspecified sum of HKD 558,000 in Cao’s account, deposited in cash. He split the money to deposit into 19 personal accounts, all using your home address to register after December 2001.

After the robbery, Gao exited the country 53 times, including 35 times to mainland China and 7 times to Macau, costing nearly 200,000 yuan.

The Cao couple bought an apartment in August 1997 and paid HKD 574,800 in cash.

Two years later, he bought an apartment, paid HK$396,000 upfront, and paid off two mortgages of HKD 388,000 in 2001 and HKD 500,000 in 2004.

Police allege that the transactions did not match a police officer’s salary and HKD 500,000 in cash of unknown origin matched the amount stolen during the 2001 bank robbery.

Three lethal cases in six years all involved Cao. As a police officer, Cao’s motives elicit much speculation.

After nearly a year of investigation and evidence collection, a Hong Kong court heard three cases on February 26, 2007.