A popular psychology professor at an Illinois college was unveiled as a teenage killer who murdered his family 46 years ago — and began an award-winning career after serving just six years for an insanity bid.

The pony-tailed professor, Dr. James St. James — the head of Millikin University’s psychology department — was outed by a Texas reporter with the Georgetown Advocate, a newspaper based in the town where St. James fatally shot his parents and 17-year-old sister on Aug. 4, 1967.

The then-15-year-old, under his born name James Wolcott, spent six years in a mental institute after being found not guilty of the murders by reason of insanity.

Courtesy Georgetown Advocate

At 15 years old, James Wolcott fatally shot his parents and teen sister. After six years in a mental institute, he changed his name and began an academic career in psychology.

“I’m just shocked, absolutely shocked,” Lana Hinshaw Klan, a videographer who took one of St. James’ classes while enrolled at the small liberal college, told CBS 2 News.

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“He really is a good guy. I have really fond memories, and I feel sorry for him, because now his life is all turned upside down.”

Courtesy Georgetown Advocate

Bedroom of Elizabeth and Gordon Wolcott. The mother woke up from the gunfire that killed her husband and daughter, but her son came to the door before she could escape and shot her three times.

And even the Decator, lll., school of about 2,400 students appears to support the 61-year-old esteemed professor.

“Millikin University has only recently been made aware of Dr. St. James’ past,” the school said in a statement. “Given the traumatic experiences of his childhood, Dr. St. James’ efforts to rebuild his life and obtain a successful professional career have been remarkable. The University expects Dr. St. James to teach at Millikin this fall.”

But a city councilman, Jerry Dawson, said the bespectacled professor should have told the school about his blood-stained past.

Courtesy Georgetown Advocate

The 22.-caliber rifle that 15-year-old James Gordon Wolcott used to murder his father, mother and 17-year-old sister.

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“I look at this from a law enforcement perspective, and I just have a problem with somebody who didn’t disclose this information,” Dawson told Reuters. “If I were a parent and my kids were going to Millikin, that’s something I would want to know.”

And St. James has been able to hide the gruesome details since the horrific triple murder rocked the sleepy Austin suburb more than four decades ago, when his parents and sister were found murdered in their home.

Courtesy Georgetown Advocate

James Gordon Wolcott, 15, at the Georgetown Courthouse on Aug. 5, 1967. He was being held for the murder of his parents and teen sister.

The teenaged James Wolcott used a .22-caliber rifle to fatally shoot his father, Gordon Wolcott — a prominent professor at Southwestern — in the living room at about 10 p.m.

The armed teen then went into his 17-year-old sister Libby’s bedroom, where he killed her with bullets to her chest and head.

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Courtesy Georgetown Advocate

Dr. Gordon Wolcott was reading in the living room when his son walked in with a .22-caliber rifle and shot him dead.

His mother, Elizabeth, burst out of her bedroom because of the gunblast — but the gun-toting teen quickly shot her twice in the head.

Cops eventually cuffed the the teenaged boy, who admitted that he planned to kill his family during his murder trial.

The young James Wolcott claimed that he knew he was suffering from mental illness, which was enhanced by his weeks of huffing airplane glue.

Courtesy Georgetown Advocate

The murdered sister, Elizabeth (Libby) Wolcott 1950-1967

He told investigators that he “hated” his family and believed that they were trying to destroy him. He blamed his mother for chewing her food too loudly and his sister’s bad accent as part of a plan to drive him mad.

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He confessed to a classmate that he was angry at his father for not allowing him to grow his hair or march in a peace rally. He said his father wouldn’t let him wear anti-Vietnam war buttons.

Courtesy Georgetown Advocate

Reporter Ann Marie Gardner of the Georgetown Advocate speaking to Dr. James St. James at a restaurant near the Millikin University campus.

Doctors later diagnosed his condition as paranoid schizophrenia and after a six-month trial an all-male jury found the teen not guilty by reason of insanity.

He was shipped to Rusk State Hospital, where he served six years before he was cut loose.

He changed his name after he was released by a jury, who took just 10 minutes to declare him sane, the Georgetown Advocate reported.

Courtesy Georgetown Advocate

A skeletal face painted on a wall in James Gordon Wolcott’s room.

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With his new identity, James St. James — who has an IQ of at least 134 — began a career in academia and started teaching for Millikin University after he scooped up a PhD in 1988, the paper reported.

St. James — who won a leadership award in 1997 — has declined several requests for comments by multiple news agencies.

But Decator’s mayor said the convicted killer should step down from his post at the school where he’s worked for more than 30 years.

“I’d hope the character of this gentleman has been such ... that he in fact will do the right thing — which, for the sake of the university, would be to resign,” Mayor Mike McElroy told the Chicago Sun-Times.

“If I had done something where I worked, I’d resign because I wouldn’t want to bring any more publicity or potential shame on the company I work for,” he said. “I hope that’s what would happen.”

But one student, Jerry Grader, told the Chicago Sun-Times that she hopes the professor can continue to teach.

“I feel comfortable with him,” Grader said. “And I do not see him as a threat to anyone.”