So-Called 'Gone Girl' Case: Ex-Classmate Says Suspect Was Studious, Person 'You See as the Next Congressman'

— -- A former classmate of the suspect in the wrongly-called “Gone Girl” kidnapping case described Matthew Muller as “friendly” -- but also serious and very studious.

“We remember Matt as being the person that you see as the next congressman or senator, sitting behind the desk in some elected capacity and certainly not in sitting in a jail cell faced with these very serious charges,” Alex Volberding told ABC News’ “20/20”

Muller, 38, has been accused of kidnapping Denise Huskins in March and is in police custody.

Volberding said he and Muller were in the same public policy program at Pomona College in Claremont, California, from 2000 to 2003.

“He was a friendly guy,” Volberding said. “He approached college with a very regimented attitude and vigor that was unlike most of our classmates.”

Muller, a former Marine, approached his studies with the “same determination, drive and diligence that one would approach boot camp,” Voldberding said, so he said he was stunned when he heard that Muller was the suspect in a kidnapping case.

“I was totally shocked,” Volberding said. “I was absolutely surprised to hear about his connection to this.”

According to a sworn affidavit, Muller served in the Marines from 1995 to 1999, attended Harvard Law School from 2003 to 2006 and later taught at the school. He also worked at the Kerosky, Purves & Bogue law firm in San Francisco, according to The State Bar of California records.

Muller, who will be disbarred, was arrested on June 5 in connection with a home invasion robbery in Dublin, California, and authorities said they have since found similarities between that case and the alleged kidnapping of Huskins.

Muller’s attorney, Thomas Johnson, said that his client is bi-polar and has a history of mental illness.

“It’s been the past five to eight years where he has, where we are seeing some difficulty conducting a normal life,” Johnson said.

But Johnson denied the kidnapping claim and his client intends to plead not guilty to all charges. When asked if he planned to use an insanity defense, Johnson said, “It’s certainly something we are going to think about.”

“It doesn’t mean it’s the only defense,” he said. “It just means it something we will think about."