Three family members who were killed during what was described as a possibly "random" triple murder-suicide attack carried out by an unrelated person at an Iowa state park last month were shot, stabbed and/or strangled, according to autopsy results released Thursday.

Tyler Schmidt, 42, died from a gunshot wound and "multiple sharp force injuries," while his wife, 42-year-old Sarah Schmidt, died from multiple sharp force injuries, the Iowa Department of Public Safety said in a news release. Their 6-year-old daughter, Lula Schmidt, died from a gunshot wound and strangulation, officials said.

The Schmidts’ bodies were discovered on July 22 inside a tent at the Maquoketa Caves State Park Campground, which is located approximately 180 miles east of Des Moines.  Their 9-year-old son, who was with his family on the camping trip, survived the attack without physical injuries, but investigators have not said whether he was in the tent when the attack happened.

The department confirmed Thursday that the killer was Anthony Sherwin, 23, of LaVista, Nebraska, who died from a self-inflicted gunshot wound after the attack on the family early on the morning of July 22 in their tent at the Maquoketa Caves State Park campground. Sherwin was at the park camping with his parents at the time of the attack, according to police and Sherwin's mother.

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Photo of Iowa family including three people murdered

In this undated file photo provided by the Schmidt and Morehead families, Tyler Schmidt and his wife Sarah pose with their children, whose faces have been blurred during a family outing.  (Courtesy of the Schmidt and Morehead families via AP)

Investigators said all evidence collected substantiates that Sherwin acted alone, but police have not indicated a motive in the killings. The release said no further information would be released Thursday. 

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Mitch Mortvedt, assistant director of the Department of Public Safety’s division of criminal investigation, told The Associated Press last month that the initial investigation had "not revealed any early interaction between the Schmidt family and him."

Photo of adult victims murdered

A photo of Tyler and Sarah Schmidt sits on the podium during the Celebration of Life event for Tyler, Sarah, and Lula Schmidt held at Overman Park on Tuesday, Aug. 2 2022 in Cedar Falls, Iowa. (Chris Zoeller/The Courier via AP)

"We don’t know what led up to this, what precipitated it," he reportedly said. 

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Adam Morehouse, Sarah Schmidt’s brother, told the news outlet the family had no connection to Sherwin and he believed it was a "completely random act."

Police who swarmed the park in the wake of the shooting found Sherwin’s body outside the campground but within a wooded area of the park.

Police officer walking in front of Iowa state park

An Iowa State Patrolman walks past a Maquoketa Caves State Park sign as police investigate a shooting that left several people dead, Friday, July 22, 2022, in Maquoketa, Iowa. The campground was evacuated in the wake of the shooting.  (Nikos Frazier/Quad City Times via AP)

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Sherwin’s mother, Cecilia Sherwin, told The Associated Press in the days after the shooting that she and her husband were devastated by attack on the Schmidts and by the loss of their son, whom she described as kind, sensitive, an exceptional student and an aspiring businessman.

The Associated Press contributed to this report. 

If you or someone you know is experiencing suicidal thoughts or a mental health crisis, please contact the Suicide & Crisis Lifeline at 988.