A police officer who passed out last week during a selection process to join the elite "Flying Tigers" unit died on Wednesday.

In a late night press conference, Police Commissioner Joe Chow expressed his deep sorrow in announcing the death of 31 year-old senior inspector Wong – who passed away six days after falling ill after taking part in a series of tests off Lamma Island:

"Regrettably, and with great sorrow we have lost him,” Chow said.

“Inspector Wong was a very capable young colleague who displayed great perseverance, and whose performance was outstanding.

“My colleagues and I feel great sorrow over his passing. We will provide all appropriate assistance and support to his family."

Chow said the officer had lost consciousness during a dive, while undergoing a series of selection tests that involved diving, swimming, and underwater swimming.

A Special Duties Unit medical team had given him emergency treatment at the scene before rushing him to Princess Margaret Hospital, where he underwent brain surgery.

But the officer's situation deteriorated, and the police commissioner said he passed, surrounded by family, friends and colleagues.

The selection process was suspended following the incident.

Chow explained that the selection process for the Special Duties Unit is a “gradual process” that includes physical fitness tests, and then selection exercises of increasing difficulty.

He said during the test in question, candidates were provided with equipment such as helmets, wetsuits and gloves.

“At every stage, candidates are asked if they are able to continue," he said.

Chow said police will investigate the incident and pass on all information to the Coroner, who will decide whether to hold an inquest.

He said the officer had joined the police force in 2016, and was promoted to senior inspector six years later. Wong was attached to the Police Tactical Unit Headquarters.

Secretary for Security Chris Tang and civil service chief Ingrid Yeung both issued statements expressing their sorrow over the officer’s passing, and extended their deepest condolences to his family.