Rockaway Township Mayor Michael Dachisen says the attack occurred around noon Sunday at Split Rock Reservoir in the Morris County community.
The Scout leader was flown to a hospital for treatment of injuries that are not considered life-threatening.
The three Scouts were rescued by searchers.
According to a statement from the New Jersey Department of Environmental Protection, after being airlifted to an area hospital, officers from the Division of Fish and Wildlife Conservation interviewed the victim, Christopher Petronino, 50, of Boonton.
The victim told officers he wanted to show the Boy Scouts a small Talus cave, which he has known about since the early 1980s. He said he had never encountered a bear.
The scoutmaster walked up to a rocky hillside, where there was a low-lying crevasse in the wall that was the entry to the cave.
After the victim entered the cave, a black bear grabbed his foot and pulled him further into the cave, according to NJDEP. The bear then bit the victim’s leg, his right shoulder, and then his left shoulder.
In an effort to thwart the bear, Petronino struck the bear twice in the head with a rock hammer. He then pulled his sweatshirt over his head and curled into the fetal position. He yelled to the Boy Scouts, who were outside the cave, to leave and get help.
The scouts called 911 with Petronino’s phone, but could not answer some of the dispatchers questions relating to location. The bear remained in the cave with the victim for a substantial amount of time. Petronino advised that he kept his back to the bear, but could hear it “huffing.”
Petronino yelled to the boys to take out any food they had and leave it at the mouth of the cave. The scouts reported that the bear eventually walked out of the cave.
A dog that was with the hikers barked at the bear. The bear then ran up a hill and away from the scene. Once Petronino heard the bear leave the cave, he then exited it and retrieved his cell phone at the mouth of the cave. He contacted emergency services to provide a better location of where he was.
The time between the Boy Scout’s call to 911 and Petronino’s call to emergency service was one hour and 20 minutes.
The victim told officers that he has never observed a black bear in that cave previously or in the surrounding area. His last visit to the cave was two or three weeks ago. The victim did not observe any ear tags or a collar on the bear. He could not estimate its size.
The victim was treated for bites and scratches to his scalp and legs.
CBS New York reports that the attack comes shortly after the end of New Jersey’s annual state-mandated bear hunt, which was extended an additional four days this year.
In October, the New Jersey Department of Fish and Wildlife briefly shut down Ramapo Mountain State Forest after eight people were chased by a black bear while hiking in the woods.
Three other hikers reported being pursued by black bears, but escaped unharmed, CBS New York reports. One hiker said a bear repeatedly approached and swatted at him, forcing him to use pepper spray to defend himself.
Officials believe that increased human interactions with the bears are linked to the recent bouts of aggression from the animals.