NY Post reports that several people were arrested for disorderly conduct and three police officers were injured after a housing project block party got out of hand. It all began around 11 p.m. Saturday when cops responded to complaints of a large group of “drunk people”.

When cops placed one person under arrest, onlookers turned on them.

Cops then used pepper spray against the crowd. The effects of the pepper-spray is captured on video posted to Instagram. The post depicts angry residents trying to flush the chemicals from their faces with milk.

After midnight, someone fired nine shots into the air from a rooftop in the housing project. Police officers suffered injuries caused by “air mail,” or objects tossed from rooftops of the Marcy Houses in Bedford-Stuyvesa.

By 12:30 a.m. on Sunday, small roving bands of angry residents were still taunting police officers in the surrounding blocks.

Four people were arrested in three incidents. Eleven people were also issued summonses for disorderly conduct.

The most serious arrest is shocking because a man actually head-butted a police officer:

Guillermo Lopez, 17, who was charged with assault on a police officer for allegedly head-butting a cop.

The police union slammed NYC Mayor De Blasio over the anti-cop violence that has been happening in the city over the summer.