NEW YORK (CBSNewYork) — There was a tense scene in Harlem early Sunday morning after NYPD officers responding to possible gunfire had bottles and other debris thrown at their vehicles.

CBS2’s Natalie Duddridge spoke to a few people that were at an outdoor afternoon cookout and gathering, which started Saturday night and went into the early morning hours.

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They said the incident was not related to protests, and the party was peaceful for hours.

But cellphone video taken at around 3:45 a.m. shows the scene getting tense when police showed up. Bottles and garbage are seen being thrown at police cruisers.

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Officers were responding to ShotSpotter technology — which alerts police to potential gunshots — at 133rd Street and Adam Clayton Powell Jr. Boulevard. Some residents said fireworks were being set off.

Officers tried to break up a group of about 500 people in the intersection, but then all kinds of debris was launched at them, causing damage to a windshield and driver’s side window.

Video shows the police vehicles back up and move away from the scene, leading the police union to call out Mayor Bill de Blasio and City Council Speaker Corey Johnson for “using a light touch” and adding they “should be held responsible for surrendering our city.”

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Retired NYPD lieutenant Dr. Darrin Porcher teaches criminal justice at Pace University. He said the city needs stronger leadership.

“The antidote to this very contentious situation is a back channel negotiation between police executives, elected officials, and community leaders. If those three entities are not willing to coalesce by a plausible strategy then we are consistently going to see a higher level of crime,” Porcher said.

There was mixed reaction from people who live around the area.

“I’m afraid to go to the window. That’s number one. Because some of these firecrackers do sound like gunshots,” resident Cynthia Young said.

“It was a peaceful gathering last night. It’s something that it needs to be looked at. It’s not always when we get together it’s always depicted as if we are ready to kill one another. Last night was peaceful, although some other occurrences happened,” another woman said.

Police said no one was arrested, but shell casings and two fired bullets were recovered at the scene.

There were no injuries to officers or people.

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Police are still investigating.