An autopsy finds that a waitress died of severe head injuries after getting her head caught in a dumbwaiter at a Wisconsin restaurant last week, police said Tuesday.

Fountain City Police Chief Jason Mork released the autopsy results for 21-year-old Brooke Baures of Chetek, a senior and standout gymnast at Winona State University in Minnesota. Baures was working at a banquet on the second floor of WingDam Saloon and Grill when the accident happened Dec. 1.

Based on witness' statements, police believe Baures was the only person who could have pressed the dumbwaiter's control button on the second floor and concluded no crime was committed in her death.

The autopsy found "extensive destruction" of the brainstem and left side of the cerebellum and concluded she died of severe head trauma. Police believe her head was almost entirely inside the cab of the elevator when it descended.

Based on autopsy results, police said they believe Baures' head "was located almost entirely inside the cab of the elevator canted slightly to her right as the cab descended. When the roof of the cab passed the sill of the second floor access, Brooke sustained fatal crushing injuries to her brainstem and cerebellum," the report said. Anyone operating the dumbwaiter had only about five seconds before the interior of the cab disappeared below the sill, police said.

The dumbwaiter has since been permanently removed.

Federal and state regulators have launched separate investigations.