Christensen is in custody awaiting a court appearance today in the June 9 kidnapping of Zhang Yingying, the 26-year-old daughter of a factory driver from China.
Since Zhang was last seen in surveillance video entering a vehicle, the Federal Bureau of Investigation, the University of Illinois Police Department and the Illinois State Police and local law enforcement have investigated her disappearance.
According to an affidavit filed by the FBI in federal court Saturday, Christensen used his phone to scan a forum on the website FetLife called "Abduction 101". Authorities say they believe she is dead, though her body hasn't been found.
Authorities previously said they used vehicle records to identify and interview registered drivers of the auto. On June 9, Zhang disappeared, only a few weeks after she had arrived in IL, to pursue studies in agricultural and environmental sciences.
The FBI it arrested 27-year-old Brendt Christensen on Friday.
She had been doing research on crop photosynthesis, which included using drones to study fields, the university's communications office has said.
Although Christensen admitted he picked up Zhang, he stated to the Federal Bureau of Investigation that he let her out blocks away from where he had picked her up.
The other main reason Zhang chose the UI, Hou said, was because she received enough money from a grant to afford to live and study here.
There are more than 300,000 Chinese students attending schools in the US, and Zhang's disappearance and now suspected death, has triggered widespread concern in China. 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. Zhang, 26, was about a month into a yearlong appointment at the University of Illinois' Urbana-Champaign campus when she vanished.
The affidavit says investigators obtained consent from Christensen's roommate to search the residence, where they seized numerous electronics, including several computers and cellphones belonging to the suspect.
On Monday, Zhang's family announced they are working with local Crime Stoppers to offer a reward of $40,000 for any information leading to an arrest, a previous police bulletin stated.
Christensen is a graduate student in Physics at the University. Lance Cooper, of the University of IL. She graduated from Beijing's prestigious Peking University a year ago with a master's degree in environmental engineering, according to a department webpage.
Those who knew her described Zhang as bright and outgoing.