“I had always wanted to quit. But I knew so much [insider information] about Ng. As far as I knew what kind of person Ng was, if I did not comply, he would find someone to assassinate me, and probably do something to my family as he knew where I lived,” Pang told police in his witness statement.

He earlier said Ng only explained the details of the plot to him at Wah Yan College, Hong Kong, on the night of December 7, 2019. Pang claimed he watched Ng, a former pupil of the prestigious school, make one of the bombs on its grounds.

Ng was arrested the next day.

Under cross-examination by defence counsel Thomas Iu Poon-shing, Pang said he became even more terrified of Ng after he learned of the plan.

“Then why didn’t you just leave and go home at the time?” Iu said.

Pang replied: “I thought Ng was crazy and [crazy enough] to have such a crazy plan. If I had gone back home, wouldn’t I be implicating my family members?”

He added he had never talked about or mentioned his involvement in the plot to his father, even after Ng was arrested.

In giving evidence, Pang said he was prepared to be arrested at some point.

Pang’s father, a former police sergeant, was already retired when his son was arrested on January 17, 2020.

Priscilla Lam Tsz-ying, for the defence, asked why Pang did not consult his father, who was an experienced officer, over his involvement in criminal offences that he said were committed under pressure from Ng.

Pang took a long pause and said: “I don’t want to make him worry.”

Both Ng and Pang pleaded guilty to a joint count of conspiracy to commit bombing of prescribed objects under the United Nations (Anti-Terrorism Measures) Ordinance.

Pang was testifying against the six defendants – Cheung Chun-fu, Cheung Ming-yu, Yim Man-him, Christian Lee Ka-tin, Lai Chun-pong and Justin Hui Cham-wing – who have denied involvement in the bomb plot.

He told the court he only learned of the option to become a prosecution witness from his fellow inmates after spending about two weeks in custody.

He said he requested to meet police officers for the first time in early February 2020 to express his intention to plead guilty and testify for the prosecution.

But officers did not tell him at the time about a potential discount to his sentence if the Department of Justice agreed to use him as a witness, he said.

Police took his statement in April 2020, Pang said, adding it was at that moment that officers told him of a possible 50 per cent cut to his sentence to reflect his guilty plea and in exchange for testifying against the defendants.

Immunity may be granted to a witness who is able to give evidence that has “significance to the prosecution of the case”, according to department documents.

But Pang said he had waited for nearly two years before receiving the department’s confirmation over the plea bargain.

Defence counsel Lam said Pang and the department underwent multiple rounds of negotiation over the period concerning what charges Pang had to admit in order to have some others withdrawn by prosecution.

In one of the letters between the parties, Pang asked the department to accept his plea in accordance to what was “agreed”.

Lam argued the wording referred to a prior agreement he made with police over giving evidence that would secure the convictions of others.

Pang disagreed, saying another inmate helped him draft the letter and he was not sure “what had happened at that time”.

The trial continues on Thursday.