Darsh Patel was out hiking with four other friends in Apshawa Preserve when the bear started to follow the group.
In an effort to get away, they scattered and ran in different directions. When four of them found each other later, they called local West Milford police, who found Patel's body.
Police say they "immediately euthanized" the 300-pound bear at the scene, where it was circling an area near the body, according to the Associated Press.
Kelcey Burguess, who heads Division of Fish and Wildlife's black bear project, told the AP that the bear was probably looking for food and may have smelled granola bars that the hikers were carrying. Wildlife ecologists say that running from a bear may incite it to give chase instinctually.
The black bear population has "grown out of control," especially in the north of state - which is where Apshawa Preserve is located, about 40 miles from New York City - according to a statement to the New York Times by Larry Ragonese, spokesperson for the State Department of Environmental Protection.
The high numbers of bears makes rare but potentially dangerous encounters more likely, even though the bears are generally not considered aggressive.
Black bears are usually fairly scared of people, but they're big enough that any encounter can end up deadly. And because so many now live in an area that's close to people and find their food in trash cans, some encounter enough people to lose some of the natural fear they have of humans.
Officials say that bear numbers peaked in 2009, at which point they created a bear hunting season to get the population under control.
They believe New Jersey's bear population is now somewhere between 1,800 and 2,400 bears.
Still, the number of dangerous encounters this year is almost 50% higher than it was last year - perhaps because of a shortage of berries and acorns that normally make up much of the animal's diet.