WATERVILLE – Occupying a corner of this small central Maine city, Colby College long has been a community unto itself, where students needn’t venture beyond the edge of their leafy campus of brick buildings and cozy dorms.

Students left their doors unlocked. Young women jogged alone, and didn’t feel a need to call for escorts when they walked to out-of-the-way parking lots on the 714-acre campus. It was as if the college lived under a big protective bubble.

That was until last week, when a stranger walked onto campus, snatched a senior and murdered her in what police say was a random act, an extremely rare occurrence in a state known for its low crime rate.

“The whole idea of the ‘Colby bubble’ is being burst,” said Drew McKechnie, a senior at the private, liberal arts school, and a friend of the victim, 21-year-old Dawn Rossignol of Medway.

After Rossignol’s Sept. 16 abduction and killing, the old rules don’t apply. Colby students now are being encouraged to run in pairs, carry whistles, buddy up when walking around campus and be alert for suspicious activity.

“I lock my door at night, which I never did in the past,” said Kate Russo, who attended a campus announcement Tuesday where police said a suspect, a 47-year-old Utah prison parolee, was under arrest.

Maine State Police said they expect the state attorney general to formally charge Edward J. Hackett with murder in the next couple of days. The arrest brought relief to the stunned and nervous campus, but also a reckoning that life would be different.

“This is Colby,” said college spokesman Stephen Collins. “Stuff like this isn’t supposed to happen here.”

Despite its reputation for being a safe “bubble,” neither Waterville – nor Colby for that matter – is immune to violence.

In 1996, a mentally ill man bludgeoned two nuns to death and assaulted two others in their Waterville convent. And in 1971, the body of Colby freshman Katherine Murphy of West Oneonta, N.Y., was found in a ravine on campus. Her death from multiple skull fractures remains a mystery.

Fifty miles away in Lewiston, a Bates College student and lacrosse team captain was stabbed to death in a street brawl in March 2002. Morgan McDuffee’s killer was convicted earlier this year.

In Waterville, investigators believe Rossignol, a dean’s list student and senior, was abducted after leaving her dorm and going to her car so she could make a morning doctor’s appointment. She was reported missing when she failed to show up for the appointment in Bangor.

After a massive search, her body was discovered Sept. 17 near a small dam along Messalonskee Stream in neighboring Oakland, about a mile from campus. Police are not saying how the young woman died.

Investigators, who tracked records of parolees who might be living in the area, located Hackett and arrested him Monday at his parents’ home in Vassalboro on a parole violation charge.

While Maine no longer has parole, it is part of an interstate compact in which parolees can be transferred between states.

Hackett’s rap sheet says the 6-foot-3, 250-pound suspect was sentenced in 1994 in Utah for kidnapping and robbery in a case stemming from another woman’s abduction in a Salt Lake City parking lot.

In that case, the suspect forced the woman into her car and ordered her to drive to Ogden, where an alleged assault was interrupted by police.

Hackett’s criminal record also shows a theft conviction in 1979, escape convictions in 1981 and 1986, and assault by a prisoner in 1994.

It was the randomness and unpredictability of last week’s crime in Maine that made it so scary, said criminal justice professor Bill McClaran of Southern Maine Community College in South Portland.

Since 1960, Maine has recorded as many as 55 homicides in a year, and as few as four, but the number usually ranges from the high teens to low 20s, McClaran said. The bulk of the killings are related to domestic violence and involve people who knew each other.

That was not the case in the Colby student’s homicide, said state police Lt. Timothy Doyle, who is heading the investigation.

While Colby President William Adams is not second-guessing the security measures in place when the killing took place, he said the tragedy serves as a reminder that students cannot let down their guard and acknowledges more security steps may be appropriate.

Adams also refuses to lose sight of the human loss to the 1,830-student Colby community. “A great deal has changed in the last couple of days,” he said.

A member of the Christian Fellowship on campus, Rossignol came from a northern Maine town that long has been a home to loggers and paper workers. She was valedictorian of her high school class and active in her church. At Colby, she seemed comfortable associating with a close group of friends.

“Dawn lived upstairs from me,” said Liz Bomze, who also works on the student newspaper. “She never had a mean word to say about anybody.”