DO NOT DO WHAT MAX IS DOING.
Maxine Hellenberger is a fictional character. In much the same way that I can depict without recommending Jamie's style of criminal investigation or Ellen's style of roleplaying or Lily's style of business practices, I absolutely do not recommend pointing your phone's camera at an arrest in progress.
Yes, you are absolutely legally allowed to to record police activity that occurs in a public place (this has been upheld time and time again in location after location), but you're going to get arrested, you're gonna get your phone confiscated and/or broken, you're going to fall down a whole bunch on your way back to the precinct, and, quite frankly, you are going to deserve every second of it.
...Well, okay, "deserve" is possibly the wrong word; "deserve" implies a moral dimension. Morals don't really apply here. It's like poking a bear with a stick - you should know that the natural response of that creature will be to maul you. Your actions are not necessarily immoral and deserving of retribution - indeed, they may very well be heroic and noble! - but bad things happening to you as a result is subsequently... correct.
Oh, and by the way, this hardened criminal is Ross Andrews, one of my fifty dollar patrons! That's right - for the low, low price of six hundred USD a year, you too could have the privilege of getting a forearm to the skull in a filthy alley behind an Indian restaurant.
Capitalism is a heck of a thing.