So, why does the other dude walk into the mace?
Just going by the photo-series, looks like the white dude was the aggressor, but that the cop was already on site when the confrontation happened. No idea what he saw, but if he walked up and saw this, well, they both look like they’re involved in fisticuffs. The security guy is clearly confronting the white guy by himself, when the other guy walks up. To me, it looks like he’s deliberately interfering with the cop. The cop’s raised hand seems to indicate he’s telling the dude, “stay back”, but he doesn’t, so leaves the cop no choice. That’s my interpretation. If they really wanted the white guy arrested, they should’ve left the security guy alone to do his job, instead of inserting themselves into it.