BROOKLYN, Iowa — The Iowa college student who was allegedly abducted by a stranger while running last month was killed by “multiple sharp force injuries,” investigators announced Thursday.

Preliminary autopsy results from the state medical examiner’s office also determined that 20-year-old Mollie Tibbetts was the victim of a homicide, the Division of Criminal Investigation announced in a press release.

The agency did not release additional details about the injuries she suffered or what caused them, but said further examination of the body may result in additional findings. Autopsy reports are confidential under Iowa law, except for the cause and manner of death.

The man charged with first-degree murder in Tibbetts’ death, Cristhian Bahena Rivera, allegedly led investigators to her body early Tuesday in a cornfield outside of Brooklyn, Iowa, the town where she was last seen in July. While investigators were confident then that the body was that of Tibbetts, the autopsy definitively confirmed her identity.

Investigators allege that Rivera abducted Tibbetts while she was out for an evening run in Brooklyn on July 18. Investigators allege he killed her and then disposed of her body in the secluded location.

Earlier this week, investigators said they were uncertain how she died pending the autopsy, and they’ve made no mention of recovering a murder weapon.

Rivera, a native of Mexico who is suspected of being in the U.S. illegally, made his initial court appearance Wednesday and is being jailed on a $5 million cash-only bond. He faces life in prison without the possibility of parole if convicted. A preliminary hearing in his case is scheduled for next week.

His attorney, Allan Richards, said Thursday that the public should give his client his day in court and not prejudge the case.

“Let’s let the process go,” he said. “The process is about truth-finding in a rational, peaceful and efficient manner. We’re only at the very preliminary stages of this matter.”

Rivera was employed at  nearby family dairy farm Yarabee Farms.

Yarrabee Farms is a small family farming operation that dates back to 1860 and has been owned for six generations by the Lang family, which is prominent in the community, farming circles and Republican politics. Manager Dane Lang said the farm had received dozens of disturbing phone calls and messages since the employee’s arrest, including threats to kill his dog and burn down his buildings.

“This is a scary situation,” he said.

His father and farm co-owner Craig Lang, a former president of the Iowa Farm Bureau who ran earlier this year for state agriculture secretary, said the farm was cooperating with investigators and had already turned over Rivera’s hiring records. He said now was not the time to debate immigration but to grieve the loss of Tibbetts, who was studying psychology at the University of Iowa.

Dane Lang said Wednesday they were stunned at the information, as Rivera worked under a different name and was a good employee who helped take care of their cows and got along with co-workers.

Even after Tibbetts disappeared on July 18 while out for an evening run in the small central Iowa town of Brooklyn, Rivera kept coming to work and “nobody saw a difference” in his demeanor, said Dane Lang, the manager of Yarrabee Farms. His colleagues were stunned Tuesday to learn that he was not only the suspect in Tibbetts’ death, but that he had a different real name than what he went by on the farm, Lang said.

“Our employee is not who he said he was,” Lang said at a news conference at the farm. “This was shocking to us.”

When Rivera was hired in 2014, he presented an out-of-state government-issued photo identification and a matching Social Security card, Lang said. That information was run through the Social Security Administration’s employment-verification system and checked out, he said.

Rivera’s defense attorney, Allan Richards, acknowledged Wednesday that his client received his paycheck under a different name and that he was uncertain of his immigration status. He said he was prepared to argue that his client was in the country legally, noting that he came to the U.S. as a minor and had worked and paid taxes for years.

“He showed up every day and he did his job. He was patted on his back. They turned a blind eye to the reality of documentation,” Richards said.

Rivera lived in a trailer owned by his employer, and is the father of a young girl. But little else is so far known about Rivera, who only came on to investigators’ radar this week.

“A major part of the investigation now is: Who is he? Where did he come from, and what has he been doing?” Iowa Division of Criminal Investigation assistant director Mitch Mortvedt said Thursday.