with a group of 1000 bikers that are spread all over the place using different routes toward Times Square. They'd need a fucking army of them. There was no need to signal for back up, and if back up isn't fucking RIGHT THERE it's useless. Since most of the bikers weren't taking part in carnage on the SUV and its occupants all he needed to do was try and stop it and still preserve his cover just as was described by John Miller here...
http://www.cbsnews.com/8301-505263_162-57606634/nyc-motorcycle-road-rage-incident-may-have-ruined-a-large-investigation/
CBS News senior correspondent John Miller, a former deputy commissioner with the New York Police Department, said on "CBS This Morning": "This is a story that starts out as not such a good day (for the NYPD) because they had a detective on the scene who was undercover, who took no action to intervene, and then waited four days to come forward and say, 'I was there.' That got worse (on Tuesday) when they reviewed the videotapes they received this week from other sources other than the YouTube video we first saw, and they see their own detective allegedly banging out the back window of the SUV during the incidents that led up to the man being dragged from the car. So that really changed the calculus from, was this a departmental matter to a criminal matter."
Turning to the police detective's undercover status, Miller said not breaking cover is one of the officer's primary jobs, but added, "that doesn't mean that you can't get in the middle and say, 'Hey guys, break it up,' or 'let's stop this.' You don't have to jump out and say, 'I am a secret police officer'. "
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Undercovers are for gathering intel, and if the 'shit hits the fan' while they're doing that their primary job is to not break their cover so they can be used again for other assignments. If the 'shit hits the fan' they're on their own. That's why it is such dangerous work. AFTER the undercover has gotten the info they need, they get out, and THEN the regular uniformed forces go in and make arrests so the undercover's true identity and mission remains unknown. It's like being a spy. Actually, in reality it is being a spy, and a spy is no longer any use as a spy if their identity and mission are discovered. That means no back up even for YOURSELF much less anyone else. But as Miller says, he wouldn't have needed to break his cover to try to stop the carnage.