(CNN) -- Confronted by police trying to arrest him for allegedly selling illegal cigarettes, Eric Garner raised both hands in the air and, with passive defiance, told the officers not to touch him. Seconds later, a video shows the officer behind him grab the 350-pound man in a chokehold and pull him to the sidewalk, rolling him onto his stomach.
"I can't breathe! I can't breathe!" Garner said repeatedly, his cries muffled into the pavement.
The video of the Thursday skirmish shows the Staten Island man lying on the ground motionless after the incident. An asthmatic, Garner was later declared dead at a nearby hospital, according to CNN affiliate WCBS. Police said he suffered a heart attack and died en route to the hospital.
"This is a terrible tragedy that occurred yesterday. A terrible tragedy that no family should have to experience," said New York Mayor Bill de Blasio, calling the video of the incident "very troubling."
Police told WCBS that 43-year-old Garner, a father of six, had a lengthy criminal history and had been previously arrested for selling untaxed cigarettes in May.
Officer Daniel Pantaleo, who is seen on video choking Garner, was put on modified assignment and stripped of his shield and gun as the New York Police Department continues to investigate the incident, WCBS reported. The chokehold tactic is prohibited by the NYPD.
In a statement, Patrolmen's Benevolent Association President Patrick J. Lynch called Pantaleo's reassignment "a completely unwarranted, kneejerk reaction for political reasons." He said the move "effectively pre-judges this case and denies the officer the very benefit of a doubt that has long been part of the social contract that allows police officers to face the risks of this difficult and complex job."
On Saturday, Garner's friends and family rallied alongside the Rev. Al Sharpton in Upper Manhattan, demanding a full investigation into Garner's death, according to WCBS.
Garner's wife was set to speak at the rally but found herself too emotional, WCBS reported.
New York photographer Joel Graham was at Saturday's demonstration, which lasted for two hours. He shared his photographs with CNN iReport, and says he captured them while walking alongside protesters who traveled from New Brighton Church to the store where the chokehold incident took place.
"This crowd was composed of good, well-meaning people who understood that peace was the only option and were adamant that things remain calm over Eric's death. I have been to protests that have been violent, but this crowd reflected who Eric was," he said.
Graham, an area resident, had a familiar relationship with Garner. "I am an urban art photographer, and I will talk to everyone on the streets of New York City," he said, explaining that he would occasionally chat with Garner while taking photos near the Staten Island Ferry.
"I had empathy for Eric and how he must have felt trying to catch his breath, and sympathy for the family. This was a heartfelt emotional protest because everyone loved Eric," he said.