Tibbetts, a 20-year-old psychology student at the University of Iowa, was found dead in a cornfield in Guersney, Iowa, on Tuesday morning, some 11 miles southeast of her hometown of Brooklyn. She vanished there on July 18 while going for a run.
Later on Tuesday police also charged Cristhian Rivera, 24, with Tibbetts’ first-degree murder. Police documents obtained by PEOPLE allege that Rivera abducted and killed Tibbetts after crossing paths with her while she was jogging.
However, it is still publicly unknown when, exactly, Tibbetts was killed and how well she knew her suspected murderer, if at all.
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An autopsy on her body was conducted Wednesday by the Iowa State Medical Examiner. Some of the initial findings were announced on Thursday, such as the nature of her fatal injuries.
But more specific information was not released, including what weapon or weapons may have been used and the extent of Tibbetts’ wounds. “Further examination may result in additional findings,” state authorities said.
“Sharp force injuries” include cuts and stab wounds, according to the University of Wisconsin’s School of Medicine and Public Health, and they are “caused by a sharp/pointed object.”
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Rivera’s arrest warrant affidavit is not more enlightening. It shows that he allegedly said he “blocked” his “memory” after Tibbetts grew unnerved by him when he began running around her.
The next thing he remembered was being in his car and then realizing that her dead body was in his trunk, her head bloody, according to the arrest affidavit.
Rivera, who made his first court appearance on Wednesday, remains in custody in lieu of $5 million cash bond.
He has not entered a plea but his attorney reiterated that he is presumed innocent and no evidence has yet been presented in court.
A motive in the killing has not been confirmed.