SEOUL, South Korea (AP) — South Korean prosecutors on Wednesday began reviewing whether to formally charge a man arrested last week on allegations that he operated secret chatrooms where he posted sexually abusive videos of blackmailed women in return for cryptocurrency payments.

The allegations have triggered intense public uproar and soul-searching over a culture that critics say is lenient about sexual violence and continuously fails the victims, prompting President Moon Jae-in to call for thorough investigation and stern punishment for operators of such chatrooms and their users.

Wearing a neck brace and handcuffed to his waist, the suspect, Cho Ju-bin, 24, was paraded before journalists at the Jongno Police Station in Seoul before officers drove him to the prosecutors’ office. Police officers created a perimeter around the station’s gate to block off angry protesters, who waved signs that read “From chatroom to prison” and “Punish all users” and yelled “Give him the highest penalty!”

“Thank you for stopping the life of a devil (I) couldn’t stop,” Cho said in front of a barrage of camera flashes.

He refused to answer questions about the accusations against him but offered apologies to a former mayor of Gwangju City, the president of local broadcaster JTBC and a freelance journalist currently on trial for allegedly attempting to blackmail the JTBC president for reasons that weren’t immediately clear. Police said they currently don’t have any knowledge linking the three men with the chatrooms.

Before sending Cho’s case to prosecutors, police said they had arrested 18 people since September while investigating private chatrooms on the Telegram messaging app, where users paid in cryptocurrency to view videos of a sexual nature that involved dozens of allegedly blackmailed women and girls.

Under the nickname “Doctor,” Cho allegedly operated one of the biggest chatrooms, with around 10,000 users, and police are investigating whether he operated others. He is suspected of using private information he secured from workers at local government offices to blackmail victims lured through fake job ads.

Police are chasing other chatroom operators, including a Telegram user who used the nickname “GodGod.”

Around 5 million people have signed online petitions filed to Moon's presidential office calling for the disclosure of personal information of all chatroom operators and customers and for their stern punishment.

On Monday, Moon called for a thorough investigation and denounced the alleged crimes as a “cruel act destroying a human’s life.”