An Illinois man accused of kidnapping a Chinese exchange student will appear before a judge Monday.
When investigators reviewed the search history on Brendt Christensen's phone, it showed he had visited a website about abduction, reports CBS News' Tony Dokoupil.
According to a criminal complaint, Zhang was on her way to meet her new landlord when Christensen allegedly approached her.
Surveillance video allegedly shows the moment Christensen pulls over to talk to Yingying Zhang. A minute later, Zhang gets into Christensen'sand they drive away.
The 26-year-old University of Illinois student was wearing a gray and pink flannel shirt and carrying a blue backpack.
At 1:35 p.m. on June 9, Zhang boarded a bus near campus and texted her new building manager to say she was running late.
At 1:52 p.m., Zhang got off a bus and tried to flag down another. Nine minutes later, she encountered Christensen.
At 2:38 p.m. the building manager texted Zhang and got no response.
University staff reported the exchange student missing that night.
Police determined the sunroof and cracked hubcap on the car in the surveillance video matched Christensen's 2008 Saturn.
"I am shocked," said Lance Cooper, Christensen's former academic adviser in the physics graduate program at the University of Illinois.
"There was nothing unusual about him. He was a bit quiet but he interacted well with the students. He was quite a good teacher," Cooper said.
During a June 15 interview with the FBI, Christensen admitted to giving an Asian woman a ride.
According to the complaint, Christensen said, "He believed he made a wrong turn, because the female became panicked."
He then claimed to let her out of the car.
During a search of Christensen's phone they discovered he had visited a forum called "Abduction 101" in April.
Investigators began monitoring Christensen's activities one day after he was interviewed.
The day before his arrest, investigators recorded Christensen explaining how he kidnapped Zhang, took her back to his apartment and held her against her will.
Zhang's family flew to Illinois after she disappeared.
"They kept their hope up until the news came out that the suspect was arrested and the FBI presumed that Yingying probably won't be alive," according to Tina Chu, who is acting as the family's translator.
She says they won't leave until Zhang is found.
"The whole purpose for the trip was to bring Yingying home. So I'm really hoping they can find their kid," Chu said.
Zhang came to the University of Illinois Urbana in April as a visiting scholar.
This fall, she planned to join the school's graduate program and get her Phd.