After the Air Force, McCullough worked as a police officer in a Washington town until the mid-1980s, when he was arrested and later convicted for having sex with a 13-year-old girl, Sycamore Police Chief Donald Thomas said.
McCullough's train alibi fell apart in 2010, when a woman he dated in 1957 was approached by police who were again looking into the slaying. While digging up an old photo of Tessier for investigators, the ex-girlfriend stumbled on an unused train ticket from Rockford to Chicago on the date of the crime, authorities said.
Through follow-up interviews, including with McCullough, "we were able to determine he was the person who had killed Maria Ridulph," said Thomas, whose department cooperated with Illinois State Police and the Seattle Police Department in the renewed effort.
Thomas declined to say whether McCullough confessed. He also said DNA played no role in the case.
Chapman said authorities approached her last year with a photo lineup that included a picture of McCullough when he was about 18 years old. She said she pointed to him as the young man who approached Maria and her that winter day.
The arrest has stirred up chilling memories among current and former Sycamore residents.
James Cliffe was 12 years old when Maria disappeared. On Saturday, he said Tessier would ask neighborhood kids to pose for photographs for him as they walked by his house.
"He said he was an artist or something," Cliffe said, calling Tessier "a weird duck."
As the days went by with no sign of Maria, tension mounted in Sycamore, Cliffe recalled.
"I remember driving around town with my dad, and there were people going door to door like vigilantes, demanding to be let in to search neighbors' houses," he said.
In Seattle on Saturday, four family members of McCullough's attended a court hearing that, in his absence, authorized the murder charges levied against him. None of them spoke in court, but outside the courthouse a man who identified himself as a friend of the family said McCullough had triple bypass surgery a few years ago.
After learning of his arrest, McCullough's stepdaughter Janey O'Connor said she grieved for Maria's family, but added that McCullough had been "an outstanding father and amazing grandfather for the 23 years I've known him."
'He's just your average guy … just an optimistic life-works-out kind of person," said O'Connor, who lives in the Seattle area.
McCullough's niece, Jenn Howton, was in shock after learning that her favorite uncle had been arrested.
She acknowledged that "other people have said crazy things about his past, but I never saw it."
"I was alone with him umpteen-million times," Howton said. "Never was he inappropriate in any way."
In Sycamore, Charles Ridulph, Maria's older brother, said he and his family were worried about having to relive the crime that took away their sibling, he said. Maria's parents, Michael and Frances Ridulph, are both deceased.
"They don't have to live through this," Charles Ridulph said. 'We struggled with this so long, but now it is happening all over again."
Reuters and Tribune reporters John Byrne, Art Barnum, Joe Mahr and John Hector contributed.