A nurse who was tubing the Apple River with family when she encountered a chaotic stabbing scene said she attempted to save 17-year-old Isaac Schuman, who died soon after.

Andrea Beldazo, a registered nurse, testified Thursday during the fourth day of the St. Croix County Circuit Court trial of Nicolae Miu, a 54-year-old Prior Lake man charged with Schuman's death and the attempted murder of four people on July 30, 2022, when Miu encountered the others while tubing on river in Wisconsin. He could face life in prison.

Beldazo's family thought Schuman's group was partying before hearing their laughs turn to screams. Beldazo said she ran through the water when she realized someone was hurt.

"It felt like forever," Beldazo said, recounting how she and others took turns giving Schuman CPR, singing "Baby Shark" to time their compressions.

"At first I thought he had been impaled on the set of roots and branches that were hanging down ... but then I looked and it was a slash mark," Beldazo said, holding back tears as she recalled the scene. "It was a long, thin and clean cut."

First to testify Thursday was Janelle Duxbury, who said she was sleeping as her tube floated along the Apple River that day before a friend woke her saying, "Hey, let's go check [that] out." Schumer's group were yelling at Miu as Duxbury walked toward them, and she said her friend Madison Coen yelled at Miu to leave.

That's when she saw Coen's head lurch to the right, causing her to stumble and walk away. She believes that is when Miu struck Coen, and when "chaos and yelling broke out."

Duxbury said her friend Dante Carlson struck Miu in the face while yelling to never hit a woman. They exchanged blows, she added, before she saw Miu walk toward Rhyley Mattison and stab her.

"He came and I thought it was a little punch towards her ribs, until he removed his hand. I saw the knife come out of my friend's side," Duxbury said. "The way he was standing there, it was a very expressionless, hollow, almost demonic look in his face ... his eyes did not look human."

Additional testimony and police body camera footage played in the courtroom depicted a chaotic scene, with some people screaming for help and stabbing victim A.J. Martin holding his intestines. Martin testified Wednesday that he spent 27 days in the hospital after the stabbing, and said he felt certain he would die.

Body camera footage from St. Croix County Sheriff's Sgt. Chase DuRand showed bystanders kneeling by Martin, clutching his hand while telling him to hold on.

Miu's attorneys have argued that their client feared for his life when he was confronted by a large group of people, and had the legal right to self defense. Many of Thursday's questions focused on that.

Responding officers testified that Miu did not smell of alcohol or show signs of impairment, adding that he did not resist arrest or claim to know about the stabbing. Attorneys also suggested that people looking for Miu after the incident could have harmed him, referencing to a specific bystander who searched for Miu while holding a baseball bat.

Attorneys questioned whether Miu struck Coen, noting that investigators could not find proof of Coen's injury, though some witnesses reported seeing Miu hit her.

Body camera footage played Thursday showed Coen exiting the river, crying as she said, "He punched me in the face."

The trial is expected to continue into next week. Lawyers expect it will end within 12 days.