On June 12, 2017, three days after Zhang was reported missing by Miao Guofang and Liyan, two of her fellow researchers in UIUC's Department of Natural Resources and Environmental Studies, police located security camera footage from a parking garage that showed her getting into a black Saturn Astra on the university campus.

"Now we know that Christensen, who had failed in his attempt to lure another young lady into his car that same morning, was disguising himself as a cop," Shi says. "Moreover, Yingying was already running late for an appointment she made with a rental manager. She didn't want to be late."

Shi and Sun met on a mobile chat group formed as a direct result of Zhang's going missing in mid-June, by mostly Chinese students in the Chicago-Champaign area who wanted to help. Sun, a physics student who had just discovered his interest in cinematography at the end of a four-year bachelor's program in UIUC, was instantly drawn to Shi's idea of filming the fast-unraveling event.

The concert was the first event Sun had filmed. Little did he know at the time that among those whom his camera had captured was Christensen and his girlfriend Terra Bullis, who by that time had been wearing a wire for the FBI for nearly two weeks. Christensen had just graduated with a master's degree from UIUC's physics department, the same one as Sun had been attending.

As Hou brought an aching silence to the venue with a guitar rendition of a song he wrote for Zhang, Christensen took Bullis' mobile and typed the words "It was me", followed by "she is gone ...FOREVER".