(CNN) - Hundreds of recently released New York Police Department emails show the lengths that officers took to keep a close watch on activists during Black Lives Matter protests that gripped the city in the wake of the deaths of Eric Garner and Michael Brown.
Undercover NYPD officers infiltrated groups of marchers and reported back to superiors with updates while also photographing activists who were seen as leaders during marches from November 2014 to January 2015.
The internal emails, obtained by attorney M.J. Williams through a Freedom of Information Law request, were first reported by the website The Appeal.
Williams said the trove of emails shows the NYPD was surveilling the entire Black Lives Matter movement.
"The assumption that the police are there to keep people like those who are participating in those protests safe is a falsehood," Williams said.
In response, the NYPD released a statement denying the allegations.
"The NYPD does not interfere with Constitutionally-protected activities, and did not investigate Black Lives Matter as a political organization or movement," according to a statement. "The NYPD was focused on ensuring the safety of the public, protesters and officers at these events."
Marchers took to the streets after the high-profile deaths of Garner and Brown. Garner, an unarmed man, was put in an apparent chokehold by an NYPD officer and later died on Staten Island, New York in July 2014. Brown, also unarmed, who was shot and killed by police in Ferguson, Missouri, a month later.
NYPD officers came out to monitor protests as marchers took to the streets in several cities following the deaths.
In emails sent by officers that mixed in with marchers, officers sent updates on locations, sometimes even emailing high-ranking members of the department, such as Thomas Galati, chief of the NYPD's Intelligence Unit.
Images of protesters were also sent around, including one of a man holding a sign that read "Jail Killer Cops" and another that read, "I Can't Breathe." The officers took notice of another man who wore a hoodie saying "Cop Watch." The mystery man was soon labeled a "coordinator" for the walkie-talkie he operated.
One of the emails released publicly Thursday shows an NYPD officer referring to some protesters as "idiots." The email came in just before 1 a.m., toward the end of an early December 2014 protest that left some participants still gathered in midtown Manhattan.
"Still idiots up in Times Square. We'll let you know," the email reads.
Other emails sent in early December 2014 show NYPD officers discussing spotting protesters with possible "swords and masks" and referring to them as "ninjas."
The NYPD said its tactics were routine.
"The communications reflected in the emails describe the movements of large groups of protesters with a focus on preventing violence or the mass disruption of traffic," according to the NYPD statement. "These are responsibilities that fit squarely within the guidelines that dictate the NYPD's lawful activities during major demonstrations that may involve disorder or impact the safety of New Yorkers."
Williams countered by saying the images collected were unnecessary.
"They're armed and collecting data about people who are identifying themselves as people who are critical of the police and they're retaining those records," Williams said.
Meanwhile, Mayor Bill de Blasio said at a news conference that he was concerned at the notion the NYPD may have been surveilling the Black Lives Matter movement, which he described as "nonviolent."
"I have no understanding of why there would need to be any monitoring so I will of course wait for the details," de Blasio said. "But they are not a security risk in any way, shape or form, so I don't know why that monitoring would have taken place."
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