Video is playing a critical part in the initial stages of the murder trial of Derek Chauvin, a former Minneapolis police officer charged in the death of George Floyd.

Video clearly showed Floyd refusing to sit in the back of a police car, which led to officers putting him on the ground, all, potentially, reasonable acts by the defendants, NBC News reported Thursday.

Prosecutors introduced as evidence footage from officer-worn body cameras, giving jurors a first look from the perspectives of the four police officers on the scene.

Chauvin defended his actions to an onlooker after pinning Floyd to the pavement with his knee for about nine minutes, based on new video played Wednesday at Chauvin's trial that, for the first time, presents his own words about the fatal incident.

Footage showed Floyd getting panic-stricken and saying he's claustrophobic as the police officers tried to push him into the squad car. "I can't breathe," Floyd said repeatedly.

According to 61-year old Charles McMillian, who pulled over to watch the encounter, he understood Floyd's statements, that he couldn't breathe, that his stomach hurt, to mean "he was in trouble and going to die."

Chauvin didn't remove his knee from Floyd's neck until paramedics arrived, McMillian said in his testimony.

Other bystanders that had gathered can be heard yelling at the officers and asking them to check Floyd's pulse, saying he was unresponsive.

The officers, including Chauvin with his knee on Floyd's neck, continue to pin him down.

McMillian said he didn't respect what Chauvin had done after Floyd was taken away by the ambulance.

"That's one person's opinion," Chauvin told McMillian. "We gotta control this guy 'cause he's a sizable guy ... and it looks like he's probably on something," he said in remarks quoted by The Wall Street Journal.

Jurors watched body-cam footage from former officer Tou Thao, showing how police appeared to ignore pleas of concerned onlookers in the moments before Floyd's death.

Prosecutors also showed jurors body-cam footage from former officer J. Alexander Kueng, a co-defendant of murder suspect Chauvin.

Kueng's footage showed he and his fellow officers pinning Floyd to the ground as Chauvin plants his knee into the man's neck.

Chauvin, 45, is charged with murder and manslaughter for the death of 46-year-old Floyd. He has pleaded not guilty to all the charges.

The most serious charge against the now-terminated white officer Chauvin carries up to 40 years in prison.