Police in Hong Kong arrested a producer Tuesday who made a documentary for government broadcaster RTHK about a July 21, 2019, mob attack on train passengers in Yuen Long.

Bao Choy, who worked on an investigative documentary showing how police were present as baton-wielding men in white T-shirts began to gather in Yuen Long ahead of the bloody attack on passengers and passers-by, was arrested at her home, RTHK reported.

Police carried out a search of Choy's home in Mei Foo, and she was taken away by officers at about 3.30 p.m., the report said.

She was arrested on suspicion of road traffic violations relating to vehicle registration searches used in the program. Her arrest has prompted fears that she is being targeted for political reasons. She was released on bail after about six hours of questioning, RTHK reported.

The Hong Kong Connection TV documentary titled “7.21 Who Owns the Truth?” showed clips from surveillance cameras at shops in Yuen Long and interviewed people who were identified in the footage.

Its airing forced police to admit they already had a presence in the town but did nothing to prevent the attack following initial denials.

Thirty-nine minutes elapsed between the first emergency calls to the final arrival of police at the Yuen Long MTR station, where dozens of people already were injured and many needed hospital treatment.

RTHK’s director of broadcasting Leung Ka-wing said the station was "afraid" and "worried" by Choy’s arrest, but would not alter its editorial policies.

“We are afraid. We are worried ... we better say we are worried, whether we can continue the way we produce accurate news as before,” Leung told reporters.

“We always stick to our principles. It’s very clear in the charter, as well as the producer guidelines,” he said.

'Extreme shock and outrage'

At least eight media organizations, including the Hong Kong Journalists Association, the Hong Kong Press Photographers Association and the RTHK staff union issued a joint statement Tuesday expressing “extreme shock and outrage” at Choy’s arrest.

The groups called on the police to make public the details of the case and justification for the arrest, and to release Choy immediately and unconditionally.

“We think this is unreasonable and a complete blow to freedom of the press,” HKJA chairperson Chris Yeung said. “There will be an immediate chilling effect, because the reporter has been working with many media, including media of different backgrounds.”

He said even the pro-China Ta Kung Pao and Wen Wei Po newspapers had conducted such investigations.

“If you are facing a prosecution because of a (car registration search) you may not dare to continue, and you may need to wait for legal issues to be clarified before proceeding,” he said.

Council Front lawmaker and former journalist Claudia Mo said it is extremely common practice for Hong Kong journalists to use car registration searches as part of their investigations.

"This is obviously a blow to freedom of the press,” Mo told RFA. “I myself have made just such a license plate query for H.K. $45 … after someone followed me in a car.”

“This is directed at RTHK, one hundred percent,” she said.

Civic Party leader Alvin Yeung agreed.

“If this isn’t retaliation, then what is?” he told journalists.

Assault on press freedom

In a statement, Britain-based rights group Hong Kong Watch strongly condemned Choy’s arrest.

The group’s policy director, Johnny Patterson, said Choy’s arrest was “nothing less than an outright assault on press freedom.”

“The police have failed to hold the perpetrators of the Yuen Long attack to account. For the victims, there has still been no justice,” he said. “Instead, they have chosen to arrest a journalist whose only crime is reminding the world of that fact.”

Democratic Party lawmaker Lam Cheuk-ting, who was injured in the Yuen Long attack, praised Choy’s professionalism, saying she had "asked all the right questions.”

"I do think that the police operation will inevitably create a chilling effect that those journalists who dare to report any wrongdoings of the government officials or the pro-establishment camp have been facing great pressure, and I urge them to stand firm and report the truth ... without fear or favor,” Lam said in comments quoted by RTHK.

Pro-government lawmaker Junius Ho, who was filmed shaking hands with white-clad men in Yuen Long on the night of the attack, July 21, last year, said journalists should not break the law while doing their jobs.