Shaquan Jefferson, 27, recorded the July 14 video at the 125th Street and Lexington Avenue station which shows Officer Colin McGuire grappling with 22-year-old Ronald Johns, apparently putting him in a chokehold at least twice.
NYPD officers are banned from using the technique.
"Once police started kneeing him in the face, I was shocked. There was no reason for them to do that," said Jefferson, who works as a messenger.
McGuire also punched Johns in the face at least twice during the video, ordering him to "stop resisting." The encounter occurred days before Staten Island man Eric Garner died following a struggle with police in which a chokehold was apparently used.
A criminal complaint charges Johns with turnstile-jumping, resisting arrest and trespassing. The complaint also says that police used pepper spray in an attempt to subdue Johns because he "flailed his arms and twisted his body to prevent Officer McGuire from putting handcuffs on him."
But Jefferson said that when he first approached Johns and the officers, Johns was facing the wall with his hands behind his back waiting for the officers to handcuff him. The officers then ordered Johns to turn around before the scuffle began.
Jefferson whipped out his cell phone and began recording when the confrontation grew violent. He said police kneed Johns in the face before he began recording. Blood is seen dripping from Johns' nose.
Bystanders are heard yelling on the video: "Why are you hitting him?" and "You busted his nose!"
"The officers should lose their job," Jefferson said. "One of them should at least go to jail."
The NYPD said it is investigating the incident.
The police confrontation with Johns and apparent use of the banned chokehold technique came days before the death of Garner, 43, whom police were trying to arrest on July 17 for selling illegal cigarettes on Staten Island.
A video shows Officer Daniel Pantaleo placing Garner, a former city Parks worker and father of six, in what appears to be a chokehold before dragging him to the ground. Garner is heard saying: "I can't breathe" several times while on the ground with police on top of him.
Pantaleo has been placed on desk duty and was stripped of his gun and badge pending an investigation. McGuire, who is assigned to Transit District 4, remains on active duty but has been out sick since the incident.
Police Commissioner Bill Bratton has ordered a "top to bottom review" of police use of force after the Garner incident.
Jefferson said he felt compelled to send his video to East Harlem activist the Rev. Kelmy Rodriquez after hearing about Garner's death.
"It reminded me of what happened to the person in Staten Island," Jefferson said.
Jefferson said he sympathized with Johns because he feels he has also been the victim of police mistreatment.
"I have been stopped and frisked for no reason maybe 11 times," Jefferson said of the controversial police tactic that was a major issue in the city's recent mayoral elections.
East Harlem Assemblyman Robert Rodriguez called the video of Johns' arrest "incredibly disturbing" and called for "procedural reforms and measures to ensure appropriate accountability."
At a forum focusing on police and community relations at the East Ward Baptist Church in East Harlem Friday, the Rev. Dr. Sean P. Gardner Sr. said "there is room for improvement" in police and community relations.
"The community doesn't trust cops and cops have concerns about the community," said Gardner.
Anthony Miranda, a retired NYPD sergeant who is executive chairman of the National Latino Officers Association, said it looked to him as if banned chokeholds were used in both the Garner and Johns' videos.
He said part of the problem may be that after court rulings regarding the use of stop and frisk, there is confusion from the public about whether the practice is still legal. It is. Both police and the public should focus on keeping situations from unnecessarily escalating, he said.
"The problem is a lack of communication, a lack of trust and a lack of understanding of the process," said Miranda. "No one should resist arrest, but the problem is that blacks and Latinos don't have confidence in the legal process."