BALTIMORE — Joanna Sullivan remembers the helicopter on a hot summer day.

Sullivan was 9, going on 10 years old, on Aug. 15, 1975, when another young girl, Gretchen Harrington, went missing in her hometown of Broomall, Pennsylvania. Gretchen, who was 8, disappeared while walking from her house to vacation Bible school.

Sullivan and her friends were at the pool when they heard the police helicopter whirring overhead. It was an unusual event in the Philadelphia suburb, also known as Marple Township, and 48 years later, she said, “the memory is so clear.”

Gretchen’s body was found two months later and her death was ruled a homicide. But the case remained unsolved and the mystery stuck with Sullivan, now editor-in-chief of the Baltimore Business Journal, who decided during the coronavirus pandemic to dig deeper into Gretchen’s disappearance. Last October, she published a book, “Marple’s Gretchen Harrington Tragedy: Kidnapping, Murder and Innocence Lost in Suburban Philadelphia,” with co-author and childhood friend Mike Mathis.

Just nine months later, after decades of silence, came a break in the case: On July 24, Delaware County, Pennsylvania, District Attorney Jack Stollsteimer announced that a suspect had been arrested. David Zandstra, 83, a friend of Gretchen’s family and pastor at a neighboring church, was charged with multiple counts including kidnapping of a minor and first-degree murder.

The news sent ripples through Broomall and beyond.

“The families of victims often say that their lives are forever altered into the ‘before’ time and the ‘after’ time,” Stollsteimer said in a statement announcing the arrest. “Gretchen’s murder created a ‘before’ time and an ‘after’ time for an entire community — and for an entire county.

“Justice has been a long time coming, but we are proud and grateful to finally be able to give the community an answer,” he said.

For Sullivan, it marked a stunning and unexpected development. Suddenly, the longtime editor was fielding phone calls from The New York Times and the BBC about a case that never made the national news in 1975.

“There was definitely surprise, a kind of disbelief,” she said.

Before and after

Like many others in Broomall, Sullivan remembers a distinct before and after in the summer of 1975.

Already a young newshound, she followed the Gretchen Harrington case closely and worried about a murderer being on the loose. Though her own parents already were relatively strict, Sullivan remembers her friends’ parents becoming more protective after the killing.

As an adult, she often pondered writing a book about Gretchen and the impact of her death that summer. She initially tried to craft the story as fiction, but quickly realized it needed to be approached from a journalist’s mindset. With family responsibilities and a busy job, it was hard to find time to invest in the research.

Then, at her 30-year high school reunion in 2013, she reconnected with Mathis, a former crime reporter who now works in communications. The two first met in middle school when they were student reporters for Paxon Hollow Junior High’s school newspaper, The Hollow Log.

Mathis was game to collaborate on the project, which took off in 2021 in the midst of the pandemic. They scheduled a phone call to make an outline and decide who to interview. Zandstra was near the top of their list.

New information after decades of silence

In 1975, Zandstra was a pastor at Trinity Christian Reformed Church, on the same block of Lawrence Road as the Broomall Reformed Presbyterian Church, where Gretchen’s father, the Rev. Harold Harrington, presided over the congregation.

The two churches collaborated on a summer Bible camp, with Trinity hosting opening exercises and the Reformed Presbyterian Church holding classes later in the day. Zandstra helped with transportation, shuttling campers between churches in a white and blue Volkswagen bus or in his green Rambler station wagon.

On the morning of Aug. 15, Gretchen left her house around 9:20 a.m. to walk to Bible school. When she didn’t show up at the Reformed Presbyterian Church an hour and a half later, her father became concerned. Zandstra was the one to call police, according to Mathis and Sullivan’s interview with him in their book.

“Either I called, or I went to Pastor Harrington’s house, and they confirmed that she had left to walk up the street,” Zandstra told the reporters. “And I said she’s not here. I must have at that point called the police.”

Now, authorities say the pastor knew more than he let on.

Police began taking a closer look at Zandstra after a tipster came forward earlier this year. The woman, who is labeled “CI #1″ in a police criminal complaint, said she was a childhood friend of one of Zandstra’s daughters and attended school with Gretchen and her sisters.

The woman told police that Zandstra groped her on several occasions when she slept over at his house. She also shared a diary entry from September 1975, in which she wrote that Zandstra tried to kidnap another friend twice.

“It’s a secret but I think he might be the one who kidnapped Gretchen,” the diary entry says. “I think it was Mr. Z.”

In July, investigators headed to Marietta, Georgia, where Zandstra now lived. In an interview with police, the former pastor initially denied seeing Gretchen on the day of her abduction, but authorities said he confessed to killing her after being confronted with CI #1′s new information.

According to a police criminal complaint based on his confession, Zandstra was driving on Lawrence Road when he saw Gretchen walking alone and offered her a ride. Rather than take her to the church, he drove to a wooded area nearby, parked the car and asked the girl to take off her clothes. When Gretchen refused, he hit her on the head with his fist and she started bleeding. Zandstra, believing her to be dead, tried to cover her body and then left.

Stollsteimer said Zandstra is in jail in Cobb County, Georgia, and has refused to waive extradition. The district attorney is seeking a governor’s warrant to bring him to Pennsylvania.

‘Why not?’

Zandstra’s arrest is the kind of outcome Marple Township Police Chief Brandon Graeff was hoping for when he agreed to let Sullivan and Mathis comb through the Gretchen Harrington case files two years ago.

“I thought, why not?” Graeff said. “We’ve been unsuccessful through the years, we had different sets of eyes on it. It was kind of a leap of faith, no doubt, because I had never met either one.”

Though police interviewed Zandstra several times after Gretchen’s disappearance, Graeff, who has been police chief in the township since January 2020 and an officer there since 1997, said the pastor was not a top suspect.

“There wasn’t, at the time, seemingly a lot of attention towards him,” he said.

Instead, many investigators believed Richard Bailey, a convicted sex offender who had already committed crimes against young girls, was the most likely culprit. Sullivan and Mathis named him a “prime suspect” in their book. Bailey was still incarcerated for other crimes when he died in November 2013.

Though no one involved in the investigation has said whether Sullivan and Mathis’ book prompted CI #1 to come forward, Graeff credits them with shedding new light on the cold case.

“I do believe in coincidences, but I don’t believe this was one,” he said.

A new chapter

In the wake of Zandstra’s recent arrest, Sullivan and Mathis are getting back to work. Their publisher has asked them to write an update with the new details. The authors, as well as police, also are looking into other unsolved cases in communities where Zandstra previously lived.

“I got a call from a woman who said that her sister and brother were haunted by a man who tried to kidnap them in 1975, in Marlboro Township,” Sullivan said. “I showed them a picture [of Zandstra], and they’re like, that’s him — so I sent them to the police.”

But in the wake of recent revelations and a renewed rush of media attention, Sullivan said she hopes most of all that Gretchen’s family finds justice and the public remembers the young girl’s life before her death.

“I really wanted this to be more than a true crime book,” she said. “I wanted it to be about the community, about Gretchen. She deserved more than she got.”

In the course of her reporting, Sullivan found the community hadn’t forgotten Gretchen. When she reached out for interviews, replies poured in from Facebook groups and church contacts.

“We talked to more people than we could possibly use in the book,” she said.

It turns out that helicopter in the sky on Aug. 15, 1975, was a shared recollection.

“I opened the book with that scene, because that’s what my memory was,” she said. “And what we discovered over the years ... is that so many people had the same memory.”