MINNEAPOLIS (NewsNation Now) — A teen cashier working at the convenience store where George Floyd spent some of his final moments testified Wednesday in the trial of the fired police officer charged in Floyd’s death.

“If I would’ve just not taken the bill, this could’ve been avoided,” Christopher Martin testified, joining the burgeoning list of onlookers who said they felt a sense of helplessness and lingering guilt over the Black man’s death.

Martin, 19, was working at Cup Foods on May 25 when Floyd entered the store to buy cigarettes. The jury watched silent security-camera video that showed Floyd dressed in a black tank top approaching Cup Food’s counter with a banana in hand, smiling and making cheerful conversation and putting his arm around a female friend. 

Martin told the jury that he made conversation with Floyd, asking him if he played baseball. Floyd replied that he played football, Martin said, “but it kind of took him a little long to get to what he was trying to say, so it would appear that he was high.”

Soon after, Martin sold him a pack of cigarettes. He told the jury he thought the bill was counterfeit and considered just letting the store deduct it from his wages, but then decided to tell his manager, who told Martin to go and confront Floyd, who had got back into a car outside.

Floyd was “just kind of shaking his head and putting his hands in the air, like, ‘Why is this happening to me?'” Martin said.

Floyd was later arrested outside.

Martin went outside as people were gathering on the curb and yelling at officers. He took out his phone and began recording, but later deleted it, explaining that the ambulance didn’t take the fastest route to the hospital so he thought Floyd died.

“I just didn’t want to have to show it (the video) to anyone,” he said.

The day started with the conclusion of testimony by a Minneapolis firefighter who voiced frustration at being prevented from using her EMT training to help Floyd.

Genevieve Hansen, one of several bystanders seen and heard shouting at Derek Chauvin as he pinned Floyd facedown outside a convenience store last May, cried Tuesday as she recounted how she was unable to come to Floyd’s aid or tell police what to do, such as administering chest compressions.

“There was a man being killed,” said Hansen, who testified in her dress uniform and detailed her emergency medical technician training. “I would have been able to provide medical attention to the best of my abilities. And this human was denied that right.”

Hansen was among several onlookers to testify to what they saw of Floyd’s May 25 death. They described their increasing frustration, anger and despair as they begged Chauvin to take his knee off Floyd’s neck.

Lawyers for Chauvin, 45, say he followed his police training and is not guilty of the charges brought by the Minnesota attorney general’s office of second-degree murder, third-degree murder or second-degree manslaughter.

The defense has argued that Floyd’s death was not caused by the officer but by a combination of illegal drug use, heart disease, high blood pressure and the adrenaline flowing through his body.

A professional mixed martial arts fighter, Donald Williams, testified Tuesday he called 911 after paramedics took Floyd away, “because I believed I witnessed a murder.”

Williams calls Chauvin a “bum” in the video, accuses the white police officer of “enjoying” his restraining of Floyd, a 46-year-old handcuffed Black man, and told jurors on Monday he believed that Chauvin was using his knee in a “blood choke” on Floyd, a wrestling move to knock an opponent unconscious.

Chauvin’s lawyers counted that Williams does not have knowledge of police maneuvers.

Darnella Frazier, the Minneapolis teenager, whose cellphone video of the arrest went viral, cried in court as she testified Tuesday.

Frazier, 18, was walking her younger cousin to buy some snacks at Cup Foods, where a worker had moments before accused Floyd of using a fake $20 bill, when she saw police arresting Floyd outside and pulled out her cellphone.

Frazier testified that she began recording the scene because “it wasn’t right, he was suffering, he was in pain.”

Minutes later, Frazier’s young cousin took her place in the witness stand, saying in a small voice she recognized Chauvin as the man she saw kneeling on Floyd.

“I was sad and kind of mad,” the girl said.

Another bystander, 18-year-old Alyssa Funari, testified tearfully that she also felt helpless to intervene when she saw Floyd struggling to breathe as Chauvin knelt on his neck and other officers pinned down his lower body.

“I felt like there wasn’t really anything I could do as a bystander,” Funari said, adding that she felt she was failing Floyd. “Technically I could’ve did something, but I couldn’t really do anything physically … because the highest power was there at the time,” she said, explaining that an officer held the crowd back.

Chauvin attorney Eric Nelson sought to use the same evidence to show that Chauvin and his fellow officers found themselves in an increasingly tense and distracting situation, with the growing crowd becoming more and more angry over Floyd’s treatment.

But witnesses also testified that no bystanders interfered with police. When Frazier was asked by a prosecutor whether she saw violence anywhere on the scene, she replied: “Yes, from the cops. From Chauvin, and from officer Thao.”

Fourteen jurors or alternates are hearing the case — eight of them white, six of them Black or multiracial, according to the court. Only 12 will deliberate; the judge has not said which two will be alternates.

The Associated Press and Reuters contributed to this report. All reporting by AP’s Steve Karnowski and Amy Forliti and Reuters’ Jonathan Allen.