Authorities also got hold of Christensen's cell phone and found that he had visited threads titled "Abduction 101", "perfect abduction fantasy" and "planning a kidnapping" on a fetish website called FetLife, according to the affidavit in the criminal complaint.
However, later when police reviewed the surveillance video footage of Zhang's last appearance, it was found the vehicle which Zhang entered had a cracked hubcap on the front passenger side, which matched Christensen's auto and made the Federal Bureau of Investigation put him under surveillance. She went missing just weeks following her arrival at the university's Urbana-Champaign campus from China in order to pursue a course in agriculture sciences. It doesn't provide details about the content of the forum.
The FBI has arrested a man they say kidnapped missing U of I scholar YingYing Zhang.
Federal authorities say 27-year-old Brendt Christensen is accused of kidnapping Zhang shortly after she stepped off a bus near the university campus.
Christensen's first court appearance is at 10 a.m. Monday in federal court in Urbana.
Zhang is observed on video entering the front passenger side of the vehicle. "Based on this, and other facts uncovered during the investigation of this matter, law enforcement agents believe that Ms. Zhang is no longer alive", the statement from the USA attorney's office and FBI said, referring to the recording and the other details discovered about Christensen.
Supporters of Zhang gathered at the University of IL on Thursday night for a walk and concert, including the missing student's family, who traveled to IL from China upon being notified of the disappearance.
University of Illinois Chancellor Robert Jones said that the entire campus community is saddened by the news.
Twenty-six-year-old Yingying Zhang was last seen the afternoon of June 9 getting into a black vehicle.
The FBI said earlier in the week that the Astra had been found.
Zhang's father has come to IL from Nanping, China, to aid in the search.
The Chinese Students and Scholars Association as among the events' organizers.
Some 5,600 Chinese are enrolled at U of I, more than at any USA college, according to government data.
Members of Zhang's family, who have arrived in the United States and followed the search and investigation closely, were advised of Christensen's arrest and the evidence, the document added.