Father of convicted Chinese scholar's killer says her death could have been prevented if university took proper action

The father of a former teaching assistant at the University of Illinois who was convicted of killing a young visiting Chinese scholar said he believes his son’s actions could have been prevented if the university counselors his son spoke to had taken proper action.

"How can somebody that is like this commit a crime like this? It makes no sense," Mike Christensen told ABC News in an exclusive interview about his son, Brendt Christensen. "Something had to have happened. Something snapped."

Watch the full story on "20/20" FRIDAY, Nov. 15 at 9 p.m. ET

Brendt Christensen was convicted of kidnapping and killing Yingying Zhang in June 2017. He was sentenced to life in prison earlier this year.

Both Zhang and Christensen attended University of Illinois’ main campus in Urbana-Champaign. Zhang was a visiting scholar studying environmental sciences.

It took a jury less than two hours to convict Christensen, as his defense attorneys admitted in their opening statement that he had killed Zhang. Rather than argue their client’s innocence, Christensen’s attorneys used the trial to dispute the gruesome details of the killing, as described by prosecutors.

"If, for some dumb reason, the jury found him not guilty -- juries do the weirdest things -- I would've tried to have him committed because you can't have somebody that can do something like this out in society," said Mike Christensen.

Earlier in 2017, Brendt Christensen sought help from the university’s mental health facility, where he described to a doctoral intern how at one point, he had been "planning" a homicide after researching serial killers.

The counseling session was video recorded and entered into evidence at Brendt Christensen’s trial.

The intern suggested Christensen have an assessment so that he might connect with one of the specialized counselors. She also discussed Christensen’s case with counseling center staff, two of whom met with him. One of them noted that there was no need for hospitalization at that time because Christensen stated that he had no current suicidal or homicidal plans or intents. Christensen was scheduled to return for another visit; he never showed up.

"For him to even admit this is not just a cry for help, it’s a huge red flag," Mike Christensen said. "Nothing happened."

Mike Christensen believes Zhang’s killing could have been avoided if counselors took action then and there. "I’m angry that it could’ve been prevented," he told ABC News’ Bob Woodruff.

He added that his son may have "schizophrenia" or "psychosis." But he has not been diagnosed with either and Christensen’s attorneys decided against using the insanity defense prior to trial. He also had no criminal record, according to investigators.

Zhang’s family, who had flown from China to attend Christensen’s trial, agrees that action from the university’s counseling center could have saved Zhang’s life. A lawsuit on behalf of Zhang’s estate was filed in June against two counseling center employees, alleging that they "acted with deliberate indifference" to the risks and warning signs presented by Christensen.

Attorneys for the counselors moved to have the case dismissed in August, on grounds that Zhang’s estate did not make a valid argument that the counselors created or increased a danger for her, and that as government employees, they are immune from lawsuits. The judge has not yet ruled on the motion.

"We will continue to support the [Zhang] family as we have throughout this ordeal, and we will defend the social workers who are named in the civil suit," said Robin Kaler, a university spokesperson in response to the lawsuit and Mike Christensen’s comments. "The professionals and staff of our counseling center are highly qualified and trained to provide care and services to students consistent with the best practices in mental health care, and we are confident they have followed these best practices."

Brendt Christensen was arrested and charged with kidnapping Zhang on June 30, 2017, roughly three weeks after Zhang was last seen on surveillance video getting into a Saturn Astra that investigators traced back to Brendt Christensen. The video showed she had been waiting at a bus stop when she got into the car.

"It took a lot of people by surprise because he was a Ph.D. candidate," FBI Special Agent in Charge Anthony Manganaro told ABC News. "It didn’t, I guess, fit what would be considered a normal profile."

The allegations and the details of the crime shocked Mike Christensen, who at first believed his son was innocent.

"He has no aggression in him," said Mike Christensen. "Very gentle, very private, and like all of us, you know, very logical people. My sons, my daughter, myself, we depend upon logic, and so, we can shove our emotions down."

At trial, prosecutors also presented undercover audio of Brendt Christensen from his girlfriend at the time, who became an FBI informant. He opened up to her while both attended a vigil for Yingying.

"You could tell that [she] was nervous while she was doing these recordings," Manganaro said of the undercover girlfriend. "He described how [Zhang] fought so hard and how she was almost supernatural in the strength in which she fought back against him."

Mike Christensen, however, believes his son was being overzealous in the audio recording, in part because Brendt Christensen was allegedly drinking alcohol.

"I can hear in his voice," Mike Christensen said, referring to the audio recording. "He was getting drunker and drunker throughout that vigil."

In the audio, previously reported on by ABC News, Christensen is heard describing how he beat, suffocated, sexually assaulted and decapitated Zhang.

"He didn’t do half of what he said," Christensen’s father told Woodruff. "It wasn’t as horrendous — I mean sure, killing somebody’s horrendous — but it wasn’t as the prosecution made out."

Woodruff pressed Mike Christensen to identify which details from his son’s admission he took issue with.

"I believe he hit her with a baseball bat. Raped her? Doubt it," Mike Christensen responded. "But also, choked her for 10 minutes? One-handed, his bad arm, 10 minutes? And she's still alive? Does that make sense to you, sir?"

Christensen’s father specifically avoided one topic when he was interviewed by ABC News in July: the location of Zhang’s remains.

"I can’t say anything about that," Mike Christensen said when asked if Brendt Christensen would reveal where he had placed Zhang’s remains. "I can’t get into that any further."

Two weeks after ABC News interviewed Mike Christensen, Brendt Christensen’s defense attorneys released information he had provided them concerning the whereabouts of Zhang’s body.

Brendt Christensen disposed of Zhang's dismembered body in three separate garbage bags, which he tossed in a dumpster outside his apartment in Champaign, according to his attorneys.

Given this information, law enforcement believes Zhang’s remains are scattered throughout a landfill in Vermilion County along the Illinois-Indiana Border.

Even with that knowledge, conducting a search of the landfill could prove challenging – especially given how much time has passed. To this day, her remains have not been found.

"It is evident that any attempt to recover Yingying’s remains would be complicated and expensive, would require government oversight and the cooperation of the landfill owners and would have no certainty of success," said Steve Beckett, attorney for the Zhang family.