NEW YORK (CBSNewYork) — The police handler for the undercover NYPD detective accused in the gang assault on an SUV driver testified in the cop’s trial Thursday.

The handler was undercover himself and was referred to in court as “Undercover 7047,” WCBS 880’s Irene Cornell reported.

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He testified that the day before the motorcycle rally that ended in the gang assault on Alexian Lien, Detective Wojciech Braszczok sent him a text message with the subject “mayhem.”

When the handler asked him what he meant, Braszczok replied that a thousand bikers were riding around the five boroughs, running red lights and performing tricks.

The handler testified that it was three days after the September 2013 assault before Braszczok came clean — sort of — admitting that he was there but didn’t see the assault. Videos recorded at the scene seem to suggest otherwise.

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Braszczok is charged with taking part in the melee, breaking a rear window near where Lien’s child sat in her car seat and then standing by and doing nothing to help as the driver was beaten bloody.

Watch The Full Video Below: WARNING — GRAPHIC IMAGES

Moments earlier, Lien, with his wife and daughter inside the vehicle, had fled the West Side Highway in his Range Rover after being surrounded by angry motorcyclists, running over one biker in the process.

Braszczok is on trial for gang assault, along with Robert Sims, who prosecutors say was caught on video in the act of stomping on Lien. A judge is deciding the case.

Defense attorney John Arlia has said Braszczok was acting as a policeman who had just seen an SUV crush a biker and that he did not go on the attack.

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Eleven men were indicted after the incident. The others have pleaded guilty to charges that include assault and riot. One of the bikers was sentenced earlier this month to a year in prison.