“Our hearts are broken,” relatives said in a statement via state authorities.
“On behalf of Mollie’s entire family, we thank all of those from around the world who have sent their thoughts and prayers for our girl,” the statement continues. “We know that many of you will join us as we continue to carry Mollie in our hearts forever.”
Tibbetts, a 20-year-old psychology student who was entering her second year at the University of Iowa, was reported missing on July 19 after not showing up for work. She was last seen alive the night before, on her regular run.
A police source said that on Tuesday, the same day Tibbetts’ remains were found in a cornfield in Guernsey, Iowa — some 11 miles southeast of Brooklyn — 24-year-old Cristhian Rivera was charged with first-degree murder in her death.
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Authorities believe Rivera abducted and killed Tibbetts after they crossed paths while she was jogging, according to an arrest warrant affidavit previously obtained by PEOPLE.
Rivera was crucially linked to a dark-colored Chevy Malibu that was seen near where Tibbetts was spotted on July 18 and, under police questioning, he allegedly admitted to dumping Tibbetts’ body, the affidavit shows. He then led investigators to where her body was hidden in a field, police have said.
He allegedly said that after encountering Tibbetts on her run, his behavior apparently unnerved her enough that she threatened to call the police — at which, panicked and angry, Rivera “blocked” his memory and later “came to” with Tibbetts’ dead body in the trunk of his car.
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Rivera appeared for the first time in court on Wednesday afternoon where he was ordered to remain in custody in lieu of $5 million bond. He did not enter a plea.
His attorney, Allan Richards, in arguing for the media to be barred from the court proceedings, noted that Rivera is presumed innocent and that no evidence of guilt has yet been presented in court. Rivera does not have a prior criminal record, Richards said.
(Richards could not immediately be reached by PEOPLE for comment.)
Rivera will return to court on Aug. 31.
A cause of death in Tibbetts’ slaying has not been released. Her autopsy is scheduled for Wednesday.
At a news conference on Tuesday announcing Rivera’s arrest, state authorities declined to discuss a possible motive. However, they said, Rivera “seemed to be drawn to her [Tibbetts] on that particular day and chose to abduct her.”
It remains unclear when, exactly, Tibbetts was killed and how well she may have known her suspected murderer, if at all.
In the weeks after she disappeared, Tibbetts’ family spoke out frequently about the case — appearing across the news media, urging the public to provide tips and, in some cases, addressing Tibbetts’ possible abductor directly.
Her mother, Laura Calderwood, said in early August that she believed Tibbetts was still alive, somewhere.
“Every day, I feel Mollie’s presence with me,” Calderwood said then. “Sometimes I just feel her sitting on my shoulder. She was an incredibly strong young woman. Mollie is lending me here strength every day, every night.”
In their statement on Wednesday, Tibbetts’ family gave their gratitude to those who have supported them and asked for privacy to mourn:
“At this time, our family asks that we be allowed the time to process our devastating loss and share our grief in private. Again, thank you for the outpouring of love and support that has been shared in Mollie’s name. We remain forever grateful.”