MINNEAPOLIS — A young woman who was 17 years old when she witnessed then-Minneapolis police Officer Derek Chauvin pressing his knee to George Floyd’s neck for minutes in May 2020 described feeling powerless as police kept bystanders from intervening before the 46-year-old’s death.

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“I felt like there wasn’t really anything I could do as a bystander,” the witness, identified only as Alyssa because of her age, told jurors. “The highest power was there, and I felt like I was failing him.”

Alyssa said she visited Cup Foods with a friend on May 25, 2020, to buy an aux cable for her phone. By the time Alyssa parked, she said police officers were already gathered outside the store with Floyd pinned beneath Chauvin’s knee.

Using her friend’s phone, she began recording the incident.

“I heard (Floyd) say he couldn’t breathe and that his stomach hurt and that he wanted his mom,” Alyssa said. “I knew initially that there was something wrong, so I started recording.”

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She said she could see Floyd losing his breath.

“He was struggling with his ability to breathe. He was focused on trying to breathe,” Alyssa said. “At first, he was vocal, and he got less vocal, and you could tell (he was dying). He was talking with like, smaller and smaller breaths, and he’d spit a little when he talked.”

Alyssa said no officers attempted to give Floyd medical aid, despite bystanders calling for a check of his pulse. On cross-examination Chauvin’s attorney, Eric Nelson, questioned Alyssa’s recollection, pointing to a police interview in which she said Floyd’s pulse was checked multiple times. She told the jury that she saw an officer touch Floyd’s wrist, but that she was unsure about whether the officer was checking his pulse because Chauvin didn’t move afterward. At one point, she said Chauvin appeared to dig his knee further into Floyd’s neck.

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Alyssa admitted to feeling increasingly angry over what she witnessed in the moment.

“I was upset because there was nothing we could do as bystanders except watch them take this man’s life in front of our eyes,” Alyssa said. She said she subsequently felt “numb” as she tried to process what she had seen.

Her testimony came on the second day of the trial against Chauvin, who faces second-degree murder, third-degree murder and second-degree manslaughter charges in Floyd’s death. Authorities arrested Chauvin in May 2020 after video surfaced on social media showing him pressing his knee to Floyd’s neck. The Hennepin County medical examiner ruled the death a homicide, determining that Floyd’s heart stopped as he was being restrained. A separate autopsy commissioned for Floyd’s family also called his death a homicide but concluded that he died of asphyxiation due to neck and back compression.

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The trial is expected to last about four weeks at the courthouse in downtown Minneapolis, which has been fortified with concrete barriers, fencing, and barbed and razor wire. City and state leaders are determined to prevent a repeat of damaging riots that followed Floyd’s death, and National Guard troops have already been mobilized.

Floyd’s death prompted global outrage and sparked a national reckoning over racism and police brutality.

Three other officers also face charges in Floyd’s death. Thomas Lane, Tou Thao and J. Alexander Kueng are charged with aiding and abetting second-degree murder and aiding and abetting second-degree manslaughter. They are expected to face juries in August.

The Associated Press contributed to this report.

Cox Media Group