@3: I suspect that the second suspect's arrest had more to do with the first accusation than the second.
There's generally no obligation to intervene in a fight. However, his encouragement could act as a threat to the victim, and therefore be assault. Under that understanding, the accusation that he didn't intervene would operate as support for the claim that he threatened the victim by way of the primary assailant.
Also, I wonder how much you can threaten a shooting spree in front of a cop without being arrested. Apparently quite a lot.
The security guys at Westlake Station did nothing to stop an assault, and that's okay. (??)
There's generally no obligation to intervene in a fight. However, his encouragement could act as a threat to the victim, and therefore be assault. Under that understanding, the accusation that he didn't intervene would operate as support for the claim that he threatened the victim by way of the primary assailant.