Police arrested 42 demonstrators yesterday during a series of protests against police violence that culminated on the Brooklyn Bridge, where a plainclothes NYPD officer was allegedly assaulted before he drew his firearm and pointed it into a crowd of protesters.

Yesterday's demonstration, one of a coordinated series of actions across the country, went relatively smoothly as hundreds of protesters marched south from Union Square, down Broadway, and into Lower Manhattan. It was, once again, on the Brooklyn Bridge that things began to get ugly.

Marchers were initially stymied by a rank of police and barricades preventing them from entering the Brooklyn-bound roadway of the bridge, but after a brief standoff, police relented, and protesters followed them up the roadway onto the bridge. Faced with merging traffic ahead and a crowd of police closing in from behind, the marchers soon retreated to the bridge's pedestrian walkway.

Most stayed on the walkway as the march crossed into Brooklyn, but many hopped the divide into the Manhattan-bound roadway, marching and running through the oncoming traffic. Some drivers honked in support of the march. At least one motorist, an unnamed off-duty police officer, was less enthusiastic.

After exiting his car and getting into an altercation with some of the protesters, the officer was struck in the face, according to a police spokesman. Marchers who witnessed the conflict say the officer drew his gun and pointed it at protesters. The NYPD spokesman confirmed that the officer drew his gun.

This scumbag just pulled a gun on a 15 year old #nypd

A photo posted by Ryan Lee Lugar (@ryanleelugar) on

Some of those arrested on the bridge were marching in a contingent that included students from schools like Brooklyn Friends School and the Brooklyn Lab Charter School.

The arrests on the bridge enraged protesters. "That's why they putting wings on you motherfuckers," one man shouted at a black officer. "Y'all are fucking house niggas!"

From there on, the tenor of the march grew increasingly tense. Protesters leaving the bridge attempted to prevent a Correction Department bus loaded with the arrestees from the bridge from moving, leading to more arrests.

As the march continued east, at Flatbush Avenue near Seventh Avenue, an officer shoved a legal observer and another woman to the ground. That woman was later hospitalized with bruised ribs.

The police spokesman said that in addition to the plainclothes officer who was punched in the face on the Brooklyn Bridge, another officer injured his knee while attempting to make an arrest. Both officers were treated for their injuries and released.

Throughout the march, several journalists appeared to be detained and arrested. But the NYPD's press office says that none of the credentialed journalists who were detained were charged.

Shortly before 9 p.m. last night, Mayor Bill de Blasio released a statement on the “reports this evening that two of our NYPD officers were assaulted by protestors," calling the alleged assaults "beneath the dignity of New York City."

"These attacks will be thoroughly investigated, and we will urge the full prosecution of the perpetrators," de Blasio said. "And any other person who might use the right to peaceful protest as cover to initiate violence, cause mayhem or incite disorder—whether against the police, the people or property of our great City—should consider themselves on notice that New York City will not stand for it."

The Mayor's Office declined to comment on the injured protester and the detained journalists. Mayor de Blasio is scheduled to deliver a speech at the University of Nebraska this evening.

The Stop Mass Incarceration Network, which organized yesterday's protests, released a statement which accused the mayor and media of spreading "outrageous lies about the protest." The group is calling for another protest outside City Hall next Thursday.

By Nick Pinto and Christopher Robbins