Just before 2 p.m., minutes before she was supposed to sign the rental agreement, the Chinese student missed a bus she tried to flag down near campus, court documents say. She walked to another bus stop, and appeared “distressed.”

Around that time, a man drove up in a black Saturn Astra with a cracked hubcap and a sunroof. Zhang talked to him through the passenger window for a minute — an exchange that was recorded by nearby surveillance cameras — then opened the door and got in.

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She disappeared after that, authorities said, and didn’t answer calls when fellow students, professors and the apartment manager called.

Now, authorities believe she is dead.

The driver of the Astra is Brendt Christensen, 28, federal authorities say. He has been charged with Zhang’s kidnapping.

The investigation unearthed another detail: Christensen had read up on abducting someone using the fetish-oriented social networking website “FetLife.” Particularly, FBI agents say, he frequented a forum called “Abduction 101.” Some of its sub threads include “abduction fantasy” and “planning a kidnapping.”

The website bills itself as a place for users to connect with other people interested in bondage, sadomasochism and more obscure sexual fetish fantasies.

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A search of Christensen’s phone showed he’d visited the site in April, FBI agents say.

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Representatives for Fetlife did not respond to an email message seeking comment Saturday. But the “Abduction 101” section had a new topic: “Brendt Christensen.”

In court documents, investigators say they presume Zhang is dead, but they have not said what led them to that conclusion. No murder charges have been filed. Christensen remained in jail early Saturday and it was unclear if he had hired an attorney.

Christensen earned a master’s degree from U of I’s physics program in May, but has no current affiliation with the university, a school spokeswoman told the Chicago Tribune.

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On Friday, University of Illinois at Urbana-Champaign Chancellor Robert Jones said the news that Zhang is believed to be dead had saddened the campus community.

“They have made an arrest, and now it is time for us as a university community to come together in support of her family and friends in this difficult time of loss,” he said.

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“There will be time for justice and for explanations in the days and weeks ahead. But in this moment, I ask each of you to keep her family in your thoughts and to make our collective focus a celebration of Yingying Zhang’s life.”

Zhang had graduated last year with a master’s degree in environmental engineering from one of China’s elite schools, Peking University Shenzhen Graduate School, according to the Associated Press. She was expected to start work on her doctorate this fall.

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Her research focused on crop photosynthesis. She used drones to study fields.

Zhang’s disappearance galvanized the Chinese Students and Scholars Association at the University of Illinois to help locate her, while also unnerving families of international students, concerned for their children’s safety.

According to the Associated Press, some 5,600 Chinese students are enrolled at the university, more than at any U.S. college. Nationwide, 300,000 Chinese students are enrolled as U.S. colleges.

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After Zhang went missing, investigators homed in on Illinois residents who owned Saturn Astras, court documents say.

They found an Astra in the parking lot outside Christensen’s apartment about a week after Zhang disappeared. He was interviewed twice by agents with the Champaign FBI office.

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At first he couldn’t recall where he’d been when Zhang disappeared, then he said he must have been sleeping all day or playing video games at the time, court documents said.

But during the second interview, he said he had actually made contact with an Asian woman that day. She was wearing a backpack and standing on a corner appearing distressed.

Christensen told the investigators the woman said she was late to an appointment, and he offered her a ride. She used her cellphone to show him where she was going, but after that things soured, according to the court documents.

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“Christensen claimed that he believed he made a wrong turn, because the female became panicked, at which point Christensen claimed that he let her out of the vehicle in a residential area a few blocks away from where he picked her up.”

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But investigators were suspicious about his story as they searched Christensen’s car and his phone.

The front passenger side of the Saturn Astra, an agent said in the court documents, “appeared to have been cleaned to a more diligent extent than the other vehicle doors … I believe that this type of action may be indicative of an attempt to conceal or destroy evidence.”

Authorities told The Chicago Tribune that the car appeared to be circling the area before Zhang’s abduction, a detail that court documents said is backed up by surveillance video. It shows the Astra passing Zhang, then turning and circling the block before slowing and coming to a stop in front of her.

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Investigators had also placed Christensen under surveillance after they interviewed him in mid-June, according to court documents. They captured an audio recording of him talking about kidnapping Zhang, bringing her back to his apartment and holding her against her will.