With her shopping bags in hand, she pushed open the door. There stood a man she knew, Jerome Isaac. He set upon her immediately, the authorities said, armed with a tank of fuel and a barbecue lighter, wearing white gloves and a surgical mask. He was angry, he would tell the police on Sunday, because he believed she owed him about $2,000 for odd jobs.
But there was no way Ms. Gillespie, 73, could have been prepared for what happened.
Mr. Isaac, 47, methodically set the woman aflame, burning her alive in the elevator of her building in Brooklyn on Saturday, only a few feet from her apartment door, the police said. He sprayed the flammable liquid in the woman’s face and over her cowering body, and then lighted a Molotov cocktail to ignite the fire.
Within minutes, Ms. Gillespie was burning to death in the narrow cab, and her assailant had fled down the stairs. The attack lasted only a few minutes, all of it captured by surveillance cameras; the sheer, calculated brutality stunned even the most hardened of homicide detectives.
Several hours later, Mr. Isaac, “reeking of gasoline,” turned himself in Sunday morning at a transit police station, and by the afternoon, the police said, he had confessed to the attack. He faces charges of first-degree and second-degree murder and arson.
Ms. Gillespie and Mr. Isaac lived less than two blocks apart in the Prospect Heights neighborhood. She had a reputation for trying to help people who were down on their luck. She gave food and shelter to the homeless and welcomed strangers into her apartment, sometimes hiring them for small tasks and chores, according to friends and relatives. That was how she came to know Mr. Isaac, they said.
Mr. Isaac was less known to neighbors. Some described him as being intelligent, well dressed and well spoken. But Mr. Isaac was mostly known for his penchant for collecting cans and bottles in the neighborhood; he was called “the recyclist.”
He hails from a large family from Trinidad, with seven siblings, according to his sister Janet Isaac, who lives in Maryland.
Ms. Isaac had not heard about her brother’s arrest when contacted by a reporter on Sunday evening. “My Lord,” she exclaimed. She said that she had not been in touch with him lately and did not know how he supported himself.
To those who knew him, Mr. Isaac did not seem like a troublemaker; the police said he had no criminal record in New York.
Rickey Causey, a nephew of Ms. Gillespie’s who had been living with her since he arrived in June from Louisiana, where he said his home burned down, said that Mr. Isaac had posted a typewritten bill on her door for his work clearing clutter from her apartment months before. Total due: more than $300.
Despite Mr. Isaac’s insistence on the money, Mr. Causey said that his aunt had not feared Mr. Isaac. “She wasn’t scared of no one,” Mr. Causey said.
He said Ms. Gillespie, whose apartment was filled with items she had collected over the years, had caught Mr. Isaac stealing things, including a VCR and a cake pan. “He was taking the good stuff,” Mr. Causey said. So, he said, she dismissed him.
Whatever transpired between Ms. Gillespie and Mr. Isaac, the detached way in which he carried out the attack was extraordinary, according to police officials who watched the surveillance footage.
While Ms. Gillespie was out buying groceries, he rode the elevator to her floor and, outfitted like an amateur exterminator, waited for her to return, the police said. As soon as the elevator delivered her, Mr. Isaac was blocking her exit.
He sprayed her face with liquid from the hose that snaked around his torso. As she turned and shrank back into a corner of the narrow cab, he doused her with it. Then he went through with his plan: He lighted the fuse on the bottle bomb in his other hand and set Ms. Gillespie aflame. She dropped to the floor, engulfed and screaming.
But Mr. Isaac was not finished yet, the police said. To ensure that Ms. Gillespie did not survive, he tossed the long-necked bottle into the elevator with her. He sprayed more of the fuel on her. Only then did he run away.
Mr. Isaac told the police that he hid out on a rooftop near his apartment and fell asleep. After he woke and wandered the streets, he learned that he was wanted, so he went to a transit police station about two and a half miles from Ms. Gillespie’s apartment building.
Paul J. Browne, the chief spokesman for the New York Police Department, said that Mr. Isaac initially admitted to having set a fire, but later confessed to the immolation of Ms. Gillespie. They found some of the equipment he had used on the roof of 571 Lincoln Place, where he said he had hidden, Mr. Browne said.
He said that Mr. Isaac had also set a fire at his own apartment a few blocks away, at 315 Lincoln Place, on Saturday afternoon. Mr. Isaac suggested to the police that he may have suffered burn wounds to his face, hands and neck in that fire, which left the top and bottom of the door to Mr. Isaac’s second-floor apartment scorched and the hall smelling of gasoline.
A next-door neighbor, Eric Charles, 42, said Mr. Isaac had lived in the building for several years and often rode a bicycle around the neighborhood collecting cans and bottles. Mr. Charles said he was shocked when he learned his neighbor had been charged with murdering Ms. Gillespie.
“I would never think he was capable of that,” Mr. Charles said.
Vernon J. Geberth, a retired commander of the Bronx Homicide Task Force, said that the way Ms. Gillespie was killed was “extremely rare” and especially torturous.
“The worst way of dying is by fire, because every nerve ending is assaulted simultaneously in the most horrific way,” Mr. Geberth said. “You have someone with pent-up anger and rage that’s so intense they don’t only want to kill, they want to see the victim suffer.”