“It’s literally the border between the Columbia community and Harlem,” said Amanda Ong, 21, a Columbia senior.

The park was long considered to be a dangerous expanse, especially after nightfall. But as crime dropped over the years, so did those fears.

College students and professionals began moving into the rapidly gentrifying section of Harlem along the park’s east side, using the land’s winding, wooded pathways to get access to the Columbia campus and its affiliated Barnard College.

The park soon flourished as a welcoming common space where academics and longtime Harlem residents could mingle, walk their dogs and frequent the weekend farmers market on its south perimeter.

But a recent rash of muggings and attacks in the park, culminating Wednesday with the fatal stabbing of an 18-year-old Barnard student, Tessa Majors, has shattered that sense of safety and jolted both neighborhoods, recalling a time decades ago when the city had more than 1,000 homicides a year.

The ages of the suspects in the case further unnerved local residents. First, a 13-year-old boy who lives in Harlem was arrested in connection with the killing. He was expected to be charged as a juvenile with second-degree felony murder, robbery and criminal possession of a weapon, police said.

The boy’s statements led investigators to two other suspects, one of whom is 14 years old and another who is believed to be the same age, officials said. One of the teenagers was detained and interviewed, and it was unclear whether he would be charged, officials said.

The other is believed to be the person who stabbed Majors and as of Friday evening was still being sought, according to a law enforcement official.

Columbia’s relationship with its surroundings has had many uneasy patches. The university, which has a huge endowment and owns scores of buildings, has been criticized by some longtime residents as a gentrifying force.

Tyrone Carter, 60, who works in a wine shop in Harlem, said that growing up in Harlem, he and his friends rarely ventured to Morningside Heights because it was “a different demographic.”

“People here lived through a heroin epidemic, a crack epidemic,” Carter said. “So being black in Harlem, some see it as invasion when young white up-and-comers start buying up buildings. I was born and raised in Harlem, and I can barely afford to live here now.”

Kevin Gates, 42, a teacher and lifelong Harlemite, said he was shocked by the killing but not surprised.

“This area may have changed cosmetically, but it’s still New York City,” he said. “Gentrification has brought an influx of restaurants and night life, so a lot of the new people moving in here see it as some playground or utopia. But some get a false sense of security and forget it is still New York City.”

Morningside Park is in a Harlem police precinct that has grown safer over the years, but crime has risen this year in the park itself.

As of Dec. 8, there had been 20 robberies inside Morningside Park or on its perimeter this year, compared to seven in the same period last year. Recently, police said, several teenagers had been arrested in a pattern of robberies in the area.

Majors was stabbed around 7 p.m. near West 116th Street at the foot of an expansive stone staircase leading up to Morningside Heights, police said. She then staggered up those stairs to the street, where she was found by a campus security guard.

On Friday, Cole Levi-Crouch, 36, a dog walker from Harlem who is in Morningside Park regularly, said he avoided all but the most lighted parts at night.

“Most New Yorkers always have their guard up, but if you’re new to New York, you may not know that,” he said. “The area has gotten a lot safer, and maybe that has created a false sense of security.”

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Maria Lopez, 61, a longtime park neighbor, gazed at the crime scene and said, “When I was growing up, and even in my 20s, you never came to this park, daytime or nighttime.”

But now, she said, many newcomers exhibit a boldness that contrasts with the wariness that some older New Yorkers retain from more dangerous times.

“People with money think, ‘I have the right to walk through here,’” she said. “Old-timers would never do that.”

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Majors’ death was met with shock and grief on campus, where students were preparing for finals.

The bright holiday lights lining its bustling College Walk area were turned off, and university officials advised students of counseling options and possible extensions for some academic deadlines.

“There’s a real sense of loss and sadness hovering over the campus. It’s palpable,” said Suzanne Goldberg, executive vice president for university life at Columbia.

While some students raised questions about how Columbia advises its incoming students about staying safe, other students at both Columbia and Barnard — a women’s college whose students basically share Columbia’s campus and course offerings — said safety briefings were standard, as was the advice to avoid entering Morningside Park after dark.

The attack also reopened long-standing questions over both racial tensions and Columbia’s relationship with more economically struggling nearby neighborhoods with many black and Hispanic residents.

Some students said they were worried less about their own safety than about the attack being used to portray Harlem as unsafe.

“A lot of response I’m getting from people is, ‘Oh, be careful of that area,’” said Ong, the Columbia senior, adding that such a response was “racially coded.”

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Matthew Lim, 22, a Columbia junior, also worried about how the news might affect the relationship between the Columbia community and longtime Harlemites.

“We know that just because of one incident, we shouldn’t make broad-stroke judgments about people who live here, but it’s hard if it affects a member of our community,” he said.

The park itself, which slopes downward toward Harlem, is clearly demarcated by an imposing rocky wall. Its playgrounds and ball fields have replaced patches that were once strewed with crack vials. And although crime has dropped in the neighborhood over the years, incidents in the park persist.

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Earlier this year, several people reported that they had been approached from behind in the park and punched by young people.

Since June, five people reported being robbed on or near the staircase at 116th Street and Morningside Drive, near the spot where Majors was killed.

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The local city councilman, Mark Levine, called the park much safer than it was 20 years ago but added that the recent uptick in robberies was “unacceptable.”

He said that some of the messages his office received from constituents after the attack were “laced with ugly and inappropriate racial comments” — some demanding the return of stop and frisk and a more aggressive style of policing more common two decades ago.

“One of my concerns arising from the young age of the suspects in this case is that there’ll be pressure on police to ratchet up aggressive enforcement on kids as young as 13,” Levine said.

This article originally appeared in The New York Times .