A preliminary report from the autopsy on Mollie Tibbetts' body determined that her death was a "homicide resulting from multiple sharp force injuries," the Iowa State Medical Examiner said.
Tibbetts, a 20-year-old student at the University of Iowa, went missing after an evening jog on July 18, sparking an extensive month-long search in the region. A body that officials believed to be hers was found on Tuesday in a rural area, hidden under corn stalks, and the autopsy confirmed her identity.
"Sharp force injuries" are those caused by pointed or sharp-edged objects, such as in stab wounds, incised wounds and chop wounds, according to the medical news site Medscape.
Cristhian Bahena Rivera, a 24-year-old Mexican man who illegally came to the United States, was charged with her murder on Wednesday after he confessed to following her on her run. In an arrest affidavit, Rivera said he remembered getting mad at her; what happened afterward was "blocked" from his memory.
When he came to, he realized he had put a bleeding Tibbetts in his trunk, and then he carried her into a cornfield and left her there, the affidavit states.
Tibbetts' tragic death and the suspect's unauthorized immigration status have thrust the story to the forefront of the US immigration debate in the past few days.
President Donald Trump and other leading Republicans have argued that this case shows the need to maintain stricter border security and kick out undocumented immigrants.
However, studies have cast doubt on the argument that immigrants commit crimes more often than others. A study published in Justice Quarterly in 2012 found that "foreign-born individuals exhibit remarkably low levels of involvement in crime." Similarly, a study from Northwestern University found no correlation between immigrants and violent crime.
Rivera has not yet entered a plea in the case and is being held on $5 million bond. He has no criminal record and had worked at a local dairy farm for four years prior to his arrest.
Rick Rahn, special agent in charge at the Iowa Division of Criminal Investigation, said the suspect's motive was unclear.
"I can just tell you it seems that he followed her and seemed to be drawn to her on that particular day and for whatever reason, he chose to abduct her," Rahn said.