NEW YORK — Emmanuel Mensah was a handsome, strongly built young man in his late 20s who immigrated to the Bronx from Ghana five years ago.

He joined the Army National Guard but returned to his apartment on Prospect Avenue in December, after graduating from boot camp with the rank of private first class.

And on Thursday night, he lost his life trying to save people from his furiously burning apartment building, one of 12 people to die in the blaze.

“He brought four people out,’’ said his uncle, Twum Bredu, who lives next door. “When he went to bring a fifth person out, the fire caught up with him.’’

Mensah was found in Apartment 15, his uncle said, but he lived in Apartment 11, with a friend of his father’s who was at home with his wife and four children.

Mensah, a decorated soldier who had been awarded a medal for marksmanship and was planning to join military police, got that family to safety, then pulled out four more people, his uncle said, before returning to the building.

He never emerged; authorities said he died of smoke inhalation.

The fire cut a deadly path through the building, with four children among the victims.

Maria Batiz was at home with her 8-month-old granddaughter when the fire swept up the stairs. Maris Orellana, who works at the Bronx Zoo Deli down the street, said Batiz was a regular customer and that this was her first grandchild.

On a GoFundMe page asking for support, Batiz’s daughter, Christine Batiz, said that while she was at work her mother watched the girl, a tiny child with big brown eyes. On Thursday night, she frantically called her daughter.

“She told me there was a fire in the building and she was trapped,’’ Christine Batiz wrote. “I never heard from her again. Later on, at around 1 a.m., I heard the news I never thought I would hear. I lost my angel baby and my best friend, my mother. The lady who birthed and would do anything for me is gone. I lost everything in a matter of minutes.’’

Around the Belmont neighborhood on Friday, the loss of four members of one family, the Stewarts, carried a heavy resonance. In all, 13 family members — cousins, uncles, aunts — all lived in the building. They had moved to New York City from Jamaica and decided to stay close.

On Friday morning, Ambrozia Stewart stood on the corner of East 187th Street and Prospect Avenue, weeping into the frigid air. She had lost her youngest daughter, Karen Stewart-Francis, 37, and three granddaughters: Kylie Francis, 2, and Kelly Francis, 7; and Shawntay Young, 19, their cousin.

“I don’t know what to do and I don’t know how to feel. I need somebody to tell me what to feel,’’ Stewart said. “Where do I go from here? Four at one time — what do I do?’’

Shevan Stewart, 44, another of Ambrozia’s daughters, said that her mother immigrated to the United States in the late 1980s, and that 19 of her family members followed her in 2004.

The family had just returned from visiting Jamaica last week.

Authorities said the fire was started by a 3-year-old boy who was playing with the burners on a stove — which he had done before, his mother told investigators. The cause was heart-wrenching, but the behavior not that uncommon.

Daniel A. Nigro, the New York City fire commissioner, said the department gets 75 to 100 referrals a year about children who have a history of playing with or being fascinated by fire.

Preschoolers and kindergartners are most likely to start fires caused by play, and are most likely to die in them, according to the National Fire Protection Association.

Four children died in the Bronx fire, but the boy who started it survived when his mother grabbed him and another child and escaped the building.