Darnella Frazier has been hailed as a hero by many for bringing George Floyd's death in Minneapolis police custody to the world's eyes and aiding the criminal prosecution by recording it in a video viewed millions of times. But her testimony in court Tuesday revealed a deep vein of trauma that haunts the teenager, whose trip to buy snacks forever altered her life.

Frazier's vulnerability was underscored when three other witnesses, who were also minors at the time, testified in the murder trial of former officer Derek Chauvin. They told the court they immediately knew something was wrong when they came upon the scene but felt helpless and feared for their safety as officers ignored their pleas to stop restraining Floyd, pushed other bystanders and shook a can of Mace at them.

Frazier recorded the longest independent video of what happened to Floyd on May 25 outside Cup Foods in Minneapolis.

"When I look at George Floyd I look at my dad, I look at my brothers, I look at my cousins, my uncles, because they are all Black," said Frazier, her voice faltering. "I have a Black father, I have a Black brother, I have Black friends. I look at that and I look at how it could have been one of them."

Hennepin County District Judge Peter Cahill allowed testimony from Frazier and the three witnesses who followed to be broadcast via audio on a livestream of the trial but prohibited video broadcast of them because they were all juveniles at the time.

The day's testimony ended with a Minneapolis firefighter who happened upon the scene while off duty. She recounted how she immediately knew Floyd needed help and desperately tried to render aid only to be rebuffed by police. Chauvin is on trial for second- and third-degree murder and second-degree manslaughter.

Frazier, 18, was 17 when she and her 9-year-old cousin, Judeah Reynolds, went to Cup Foods to buy snacks. She recounted how she ushered her cousin inside the store to protect her while she positioned herself near the back of a squad car and used her cellphone to record Chauvin kneeling on Floyd's neck for more than nine minutes.

"I've stayed up apologizing and apologizing to George Floyd for not doing more and not physically interacting and not saving his life," said a tearful Frazier. "It's not what I should have done; it's what [Chauvin] should have done."

Frazier refrained from wiping her tears away as jurors listened, many of them looking on sympathetically, according to reporters in the courtroom.

Frazier, dressed in a blue pantsuit, also testified that Chauvin had a "cold look — heartless. It didn't seem like he cared."

Special Attorney for the State Jerry Blackwell showed Frazier a still image of Chauvin as he knelt on Floyd's neck taken from her video. He asked her if she recognized him.

"Yes," whispered Frazier as she struggled to speak. "Yes, yes, this was the officer that was kneeling on George Floyd's neck."

Defense attorney Eric Nelson was brief in his cross-examination, crafting questions to set the scene as growing increasingly hostile and creating a potential threat to the officers. Former officer J. Alexander Kueng knelt on Floyd's back while colleagues Thomas Lane knelt and held onto his legs and Tou Thao kept a crowd at bay. The three are set to be tried together Aug. 23 for aiding and abetting second-degree murder and manslaughter.

Frazier agreed with Nelson that bystanders were getting louder and angrier, but added that no one was threatening Chauvin.

Nelson also worked another part of his defense aimed at showing that the police encounter with Floyd was more extensive and complex than the final portion bystanders witnessed.

"It's fair to say … as you approached them, Mr. Floyd was already in that position, he was on the ground and anything that happened prior to that you wouldn't be privy to or know what happened?" he asked.

"Correct," Frazier said.

Nelson has argued that Floyd was resisting arrest, posed a possible threat to officers and likely died of a drug overdose and pre-existing health conditions, including heart disease.

Reynolds briefly took the stand next, testifying that Chauvin had his knee on Floyd's neck until paramedics arrived.

"They asked him nicely to get off of [Floyd]," Reynolds said.

Blackwell asked her how Chauvin responded.

"Still stayed on him," she said. "… I was sad and kind of mad and it felt like it was stopping his breathing and it was hurting him."

Nelson declined to cross-examine Reynolds.

Alyssa Funari, 18, also recorded the incident and echoed much of Frazier's testimony, but noted that Chauvin added more of his weight onto Floyd's neck as he struggled. She testified that she told Chauvin to get off Floyd, and that he remained kneeling while a paramedic checked Floyd's neck for a pulse; none was found.

Assistant Attorney General Erin Eldridge played Funari's video in court, which captured her pleading with officers to relent. Funari grew emotional at one point during her testimony.

"Alyssa, why is this difficult for you to talk about?" Eldridge asked.

"It was difficult because I felt like there wasn't really anything I could do," she said. "As a bystander I was powerless there, and I was failing to do anything."

Kaylynn Gilbert, 17, testified she had gone to Cup Foods with her friend, Funari. She described how Chauvin grabbed a can of chemical irritant and shook it at bystanders while kneeling on Floyd.

"Scared," she said of her reaction, her voice beginning to falter with emotion, "because I didn't know what was going to happen. I was scared of Chauvin."

The second day of testimony began Tuesday with a key witness, Donald Williams II, back on the witness stand. Williams testified Monday that his experience as a mixed martial arts trainer and fighter told him Chauvin was using a "blood choke" to squeeze the life out of Floyd.

Nelson pressed Williams Tuesday about the mechanics of the move in an attempt to dispute the prosecution's assertion that Floyd died from oxygen deprivation. He asked if a blood choke is typically applied to the side of the neck and protects airflow in the trachea. Williams said Nelson was confusing his chokeholds.

Nelson asked if Williams grew progressively angry at the scene.

"You can't paint me as angry," Williams said.

The day ended with testimony from Minneapolis firefighter Genevieve Hansen, 27, who happened upon the scene on her day off.

"I identified myself right away because I noticed that he needed medical attention," said Hansen, a two-year member of the Fire Department. "It didn't take long to notice that he had an altered level of consciousness. My attention moved from Mr. Floyd to, 'How can I gain access to this patient and give him medical attention or provide direction to the officers?' "

She was repeatedly rebuffed by Thao.

"There is a man being killed," she said, "and I would have been able to provide medical attention to the best of my abilities, and this human was not provided that right."

"How did it make you feel?" asked Assistant Attorney General Matthew Frank.

"Totally distressed."

"Were you frustrated?" he asked.

"Yes," Hansen said as she began to cry.