MINNEAPOLIS - The third day of testimony in the trial of former police officer Derek Chauvin, charged in the death of George Floyd, followed a theme from Days 1 and 2: Witnesses have expressed regret over not doing more to help the Black man who died after the White officer knelt on his neck for nine minutes.

One of the most striking moments on Wednesday involved Charles McMillian, who dropped his head down and hit the desk as he wiped away tears from his behind his white-framed lenses.

As Floyd was being detained by police, McMillian said he told him: "Get on in the car because you can't win."

McMillian said he was trying to make the situation with Floyd easier based on his own interactions with police.

He said he understood that once placed in a police car, "You're done."

Floyd can be heard in the video saying that he's scared and claustrophobic as officers continued to force him in the car.

McMillian can be heard off to the side, telling Floyd he was going to have a heart attack based on how he was responding to officers.

"Mama! Mama! Mama," Floyd cried out on the video. "Oh my God. I can't believe this."

During his testimony, McMillian, 61, dropped his head down and hit the desk before him with a clenched fist of anguish as he wiped away tears from his behind his white-framed lenses.

"I feel helpless," McMillian said, explaining his reaction to reliving the last moments Floyd would be alive. "I understand him."

A brief recess followed his testimony.

Chauvin is charged with second- and third-degree murder and second-degree manslaughter. The Minneapolis Police Department fired him after Floyd's death. The three officers who accompanied Chauvin on the May 25 call - Alexander Kueng, Thomas Lane and Tou Thao - are charged with aiding and abetting murder and manslaughter. Those officers, who were also fired, are scheduled to stand trial in August.

Earlier Wednesday, prosecutors presented surveillance footage in Chauvin's trial from Cup Foods that showed Floyd in the store minutes before he died in police custody.

Chris Martin, a store clerk at Cup Foods, testified that he briefly chatted with Floyd about him playing football, immediately noticing his height. Martin said Floyd had come to the store for repairs on his phone.

Later, Martin testified that he sold Floyd a pack of cigarettes. When he held up the $20 bill Floyd handed him, the store clerk said he guessed the money was counterfeit because it had a blue hue to it. Under the store's policy, accepting counterfeit money meant it would be taken out of the clerk's paycheck, but Martin took it anyway.

Martin recounted to prosecutors that his manager "told us to go out to the vehicle and ask him to come inside to discuss what just happened."

Shortly thereafter, Chauvin and other officers arrived.

Chris Martin, a store clerk at Cup Foods, said Floyd appeared to not want to have an interaction with him about the $20 bill Martin figured to be fake.

"He just seemed like he didn't, like, want this to happen," Martin told the court. He added: "He was just kind of like, 'Why is it happening?' "

Martin said he did not say much to Floyd directly, speaking mainly with the person in the passenger seat of Floyd's vehicle, parked across the street from the store.

"Really, he kind of shook his head," Martin recalled of the moment, referring to Floyd.

Minutes later, Martin testified, he came outside the store to see Chauvin resting his knee on the "motionless, limp" Floyd.

"I saw Derek's knee on George's neck on the ground," Martin said to prosecutors. "George was motionless, limp."

When Martin first saw the events outside the store, he testified, he called his mother to tell her not to come down from their home above Cup Foods. Then he started filming the incident - a recording he said he did not keep.

Martin recalled noticing the route the ambulance took leaving the store. He said that because paramedics were taking the long way to the hospital, that had indicated to him that Floyd had died.

The clerk expressed regret Wednesday for a death he said he believes stemmed from their exchange inside the store.

"If I would have just not taken the bill, this could have been avoided," he said.

During cross-examination with Chauvin's defense team Wednesday, the Cup Foods store clerk testified that he was doing Floyd "a favor" by accepting a $20 bill the employee figured to be fake.

"I thought that George didn't really know that it was a fake bill, so I thought I'd be doing him a favor," Martin told Chauvin attorney Eric Nelson.