When investigators found the body of 21-year-old Dawn Rossignol along a rocky stream in Oakland last fall, they had hoped the death was the result of a tragic accident.

Investigators initially thought that, with no obvious cause of death, perhaps the Colby College senior had slipped and fallen on the sharp rocks that lined the stream while collecting water samples for a biology class she was supposed to attend the day she disappeared. Maybe she had hit her head and drowned in the shallow stream.

“If that wasn’t the case, we knew the implications were pretty scary,” said William Stokes, head of the criminal division for the Maine Attorney General’s Office.

But soon enough, investigators received the dreaded call from the state Medical Examiner’s Office. The young woman from Medway had been sexually assaulted. It was a homicide.

Detectives launched what would turn into one of the largest homicide investigations in recent memory.

That was eight months ago. In March, 47-year-old Edward Hackett of Vassalboro pleaded guilty to Rossignol’s murder and was sentenced to spend the rest of his life in prison.

This week, Stokes and Maine State Police Lt. Timothy Doyle, who led the investigation, sat down to talk about the massive police inquiry that involved unprecedented cooperation among 11 law enforcement agencies, and how tireless detective work and a little luck combined to solve the case in a week’s time.

Rossignol, an honor roll student with plans to become a pharmacist, disappeared early on Monday, Sept. 15, 2003. She was supposed to have met her mother in Bangor for breakfast and a doctor’s appointment and then return to Waterville for a biology class.

But she never made it to Bangor, and her body was found the next day a short distance from her car, just down the road from the Colby campus.

By Wednesday morning, hundreds of police officers, game wardens, and even police cadets from the Criminal Justice Academy were combing the fields and woods that surrounded what had become a crime scene.

Perhaps one of the scarier moments for investigators occurred that day when searchers found a white flag, stuck to a pole with electrical tape, near the railroad tracks just 200 yards from where Rossignol’s body was found.

In red crayon were written the words, “The world may never know.” On the back was a rough drawn map that police thought could have indicated Colby College and the crime scene on the Rice Ripps Road.

“Then we thought, ‘Oh God, what are we dealing with here?'” recalled Stokes. “I mean we’re now thinking we’ve got somebody toying with us. Taunting us. And we’re a few hundred yards away from a college campus.”

A stack of bulging manila envelopes stuffed into a cardboard box is testimony to the amount of time investigators spent photographing, cataloging and testing hundreds of items from the area determined to be the crime scene.

“I mean, we had the worst-case scenario here. We had a young woman abducted from a college campus, sexually assaulted and killed, and we had an outdoor crime scene. The majority of our homicide cases can be explained as soon as you get on the scene. That certainly wasn’t the case here,” said Stokes.

There are literally dozens of pictures of discarded cigarette butts, cigarette packages, used condoms, footprints, candy wrappers and tire tracks.

“Of course, in the end, none of this stuff was related to the crime, but when you are conducting an investigation of this magnitude, every single one of those cigarette butts has the possibility of solving this crime. Nothing can be overlooked, and the hours put into that search by so many dedicated people still amazes me,” said Doyle.

In the end, the flag was one of those items that initially terrified investigators, but turned out to be a clue from a treasure hunt that nearby residents had once staged in the area.

At the Oakland Police Department, detectives were combing through files of known sexual offenders in the area, compiling what would become a long list of potential suspects.

“We’d develop the list and then we’d send them out in teams with the orders to come back with that person either ruled in or ruled out,” Doyle said.

Meanwhile, the normally peaceful communities of Waterville and Oakland were up in arms. Local school officials talked of canceling activities and parents of Colby students were calling from around the country, fearing what might happen next.

“We had this precarious balance. We didn’t want to tell the public too much, because that could eventually hurt our chances of a successful prosecution,” Doyle said. “I didn’t want to alarm them either, but we did need to let them know that we were dealing with a very dangerous situation.”

Back in Augusta, forensic chemists were working around the clock, examining every inch of Rossignol’s car and clothing, searching for any evidence that could be linked to the killer.

Stokes and Doyle were among those who worked many hours each day with a nagging fear.

“This was looking more and more like a random crime,” said Stokes. “We knew we needed a break and we needed it fast. Every day we lived in fear that we would end up with another victim before we solved this case.”

It was a probation officer who was searching his list of clients for potential suspects who stumbled upon Edward Hackett’s folder.

“He came in and said, ‘Here is a guy we should check out,'” recalled Doyle.

That was Friday.

Hackett had moved back to Maine recently after having been released on parole from a Utah prison. He had served time there for abducting a woman at knife point and sexually assaulting her. The woman, it was later learned, had a hairstyle similar to Rossignol’s and also drove a red car. A police officer interrupted the attack in Utah. Hackett has since admitted to fantasizing about women with blond hair parted in the middle.

Another probation officer interviewed Hackett at the home of Hackett’s mother.

“He came back literally shaking. He said Hackett had fresh injuries to his head and arms and admitted to being in the area of the college on the day Rossignol disappeared,” said Doyle.

That night two state police detectives, Anna Love and Joe Zamboni, interviewed Hackett again, and he willingly provided a DNA sample in the form of a saliva swab.

Meanwhile, other investigators confirmed that Hackett had missed a counseling appointment the morning Rossignol disappeared.

Agents from the Maine Drug Enforcement Agency were assigned to watch Hackett 24 hours a day over the weekend.

Back at the crime lab, a forensic chemist swabbed the doors of Rossignol’s car, “even though there was nothing there that you could see. DNA has progressed so far that you can get DNA from things you can’t even see. In this case, they received a DNA sample from the handle of the car door because he had touched it when he abducted her from the parking lot at Colby. What he left behind was skin cells,” Doyle said.

On Monday morning, Doyle received a call from the lab that the DNA from the car door matched the sample from Hackett. The problem, however, was that the match set a probability standard of one in 50,000, an extremely low match in the world of DNA.

When police interviewed Hackett again, Zamboni told Hackett about the match and Hackett vomited, confessed and was taken into custody.

Still, detectives and prosecutors were worried the DNA sample would not hold up well in court, and there were issues surrounding Hackett’s confession that could result in it being suppressed as evidence from the trial.

“Then one night I was in the car and almost home. It was nine o’clock and the earliest I had been home in two weeks. The phone rang and it was Bill Harwood from the crime lab and he said, ‘How’s a DNA match of 39 trillion to one grab ya?'”

Doyle wipes a tear from his eye. “I still cry when I think about it. I literally started to cry on the phone. I said, ‘Bill, don’t take this the wrong way, but I think I love you.'”

The next day, before a standing-room-only crowd at the field house on the Colby College campus, Doyle announced the arrest.

Hackett eventually would go on to confess during a media interview, despite his lawyer’s objections, and to ask the sentencing judge to put him away for the rest of his life.

On Sunday, May 23, between 400 and 500 students of the Colby College Class of 2004 will graduate on the library lawn on the campus.