Activists who occupied the Albuquerque mayor's office in protest of police shootings say video footage exonerates a university professor who is accused of assaulting a police officer during the protest.

David Correia, 45, who teaches at the University of New Mexico, has been charged with battery on a police officer – a felony – over a confrontation during the 2 June sit-in.

Video footage contradicts the police version and establishes that Correia posed no threat when the officer grabbed him and hauled him away, several activists said on Monday.

The group Photography Is Not A Crime, which documents alleged police abuses, on Sunday posted footage of the confrontation and other incidents during the sit-in, drawing on cellphone video shot by several activists.

About two dozen activists, including relatives of people killed by the police, occupied the office of mayor Richard Berry last week, prompting acrimonious exchanges with officials and the cancellation of a city council meeting.

Twelve people were charged with criminal trespassing, unlawful assembly and interfering with a public official or staff.

A thirteenth, Correia, was charged with assaulting Chris Romero, a police officer attached to the mayor's office. According to the criminal complaint the professor “hit him with his body in his chest area, causing (Romero) to lose his balance.” The complaint adds: “When David hit Officer Romero he pushed him back which allowed the rest of the protestors to enter the office.”

In a segment of video shot by Caden Rocker, Correia and several other activists were already inside the lobby when the incident occurred. Correia was addressing other members of the group, declaring “a public meeting in a public office,” when he became tangled with Romero. Correia turned his back from the officer and held his arms in the air, still addressing his companions, when Romero pulled him down a corridor.

“I was surprised when the officer started dragging David,” said Rocker. “And I was shocked after the fact when David was charged with these phoney charges.” Charlie Grapski, another activist who compiled the clips, said the officer was the aggressor.

Correia appeared at his first hearing at the metropolitan court last week and pleaded not guilty. “These charges have no merit,” he told the Guardian on Monday. He may not leave the county or attend city council meetings – which are held in the same building as the mayor's office – until the case is resolved.

The district attorney's office said in a statement it was considering whether it would be “appropriate” to bring the case to a grand jury. “While it would be inappropriate to discuss any specific evidence, we will be reviewing all documentation and evidence that is submitted to us by law enforcement.”

The case was the latest twist in the campaign to reform Albuquerque's police department in the wake of 25 fatal shootings since 2010. Simmering anger erupted into coordinated protest in March after a video surfaced showing police shooting James Boyd, a mentally ill homeless man.

Last month activists took over a council meeting and attempted a symbolic citizens' arrest of the police chief. They staged a silent protest at a subsequent council meeting, prompting guards to escort them out. The 2 June sit-in caused a third disruption to the city council.