Often, he says he would hang back to help make sure equipment was getting to those at the front, helmets and masks passed from person to person in a massive human chain through the protest lines, or to ensure that there was a clear path of retreat for when the police inevitably charged.

On that day in August, amid pouring rain that had hampered police officers’ use of tear gas, Ivan was heading back to the van his protest cell was using to transport supplies. It was only a couple of blocks away, but as he jogged over, he turned onto a side street and suddenly found himself facing a new line of protesters that had splintered off from the main group. Looking behind, he saw a corresponding line of heavily-armed riot police, with a red warning banner held up over their heads.

“It was very bad timing,” Ivan told CNN, which has agreed to identify him by a pseudonym so he could speak without fear of further repercussions from the police.

“They started charging - and that’s how I got arrested.”

In that, he is by no means alone. Since the protests escalated in June, more than 6,100 people have been arrested for a range of offenses - including taking part in unlawful assemblies like the one Ivan attended.

Almost a thousand people have been formally charged so far, but the number is expected to rise, as are arrests, as police pour over the reams of evidence amassed throughout the past six months.

The unrest began with largely peaceful mass marches against a proposed extradition bill with China. Though the bill has since been withdrawn, the initial protests unleashed a torrent of anger and frustration with Hong Kong’s political system. Since June, protesters have demanded an investigation into allegations of police brutality and called for greater democracy.

The early demonstrations were legally-approved marches, however, almost everyone who has attended protests in recent months has been at an event deemed unlawful. Many may be guilty of rioting, due to the offense’s broad legal definition, or of violating a ban on facial coverings at public assemblies, which city leaders introduced by invoking rarely-used emergency powers.

The number of people potentially eligible for arrest could number in the hundreds of thousands.

Many of those already arrested, like Ivan, are in their twenties, or even younger. They have been the drivers of the protest movement but have also borne the brunt of the reaction and could be the ones ultimately paying the cost -- an entire generation criminalized, in a fight for their future which could end up costing them just that.