There is no guarantee this is an arrest.
These people are not showing that they are law enforcement. For all we know we just watched someone get kidnapped by sex traffickers.
Bystanders shouldn't stand by idle, if someone is getting kidnapped right in front of you, and you're able bodied, you should do something about it, violently. Even if it means grabbing the closest heavy thing and throwing it at them. Yell, make a scene, yell out "kidnappers help me!" ....etc
NEVER LET YOURSELF OR SOMEONE ELSE BE TAKEN TO A SECONDARY LOCATION. EVER.
Anything your captors are willing to do in public is only a fraction of what they would be willing to do in private.
You don't necessarily have to put yourself in harms way, but you can still show some level of resistance to kidnappers, rapists, and the rest. No one should just let those things happen in front of them, and simply pull their phone out to film.
That's some psycho pass level shit.
There's no guarantee it's even the police. Could be sex traffickers for all you know.