A Chinese immigrant who neighbors said struggled to survive in America was arrested Sunday on five counts of murder in the stabbing deaths of his cousin's wife and her four children in their Brooklyn home — using a butcher knife.

The suspect, 25-year-old Mingdong Chen, implicated himself in the killings late Saturday in the Sunset Park neighborhood, police said.

A New York Police Department (NYPD) vehicle is seen near the scene of a stabbing incident at a Brooklyn residence, in New York October 27, 2013. Five people died in the incident, according to local media. [Photo/Agencies]

"They were cut and butchered with a kitchen knife," said Chief of Department Philip Banks III.

Two girls, 9-year-old Linda Zhuo and 7-year-old Amy Zhuo, were pronounced dead at the scene, along with the youngest child, 1-year-old William Zhuo — all attacked in a back bedroom, police said. Their brother, 5-year-old Kevin Zhuo, and 37-year-old mother, Qiao Zhen Li, were taken to hospitals, where they were also pronounced dead.

Chen is a cousin of the children's father and had been staying at the home for the past week or so, Banks said.

Chen came to the United States from China in 2004, the chief said, but neighbors say he could never hold down a job.

"He made a very soft comment that since he came to this country, everybody seems to be doing better than him," the chief said. "We're not really sure what that means."

The chief said Chen still speaks only Mandarin Chinese despite being in the U.S. for almost a decade.

On Saturday night, Chen apparently had been acting in a "suspicious" way that concerned Li, Banks said. She tried to call her husband, who wasn't home, but couldn't reach him.

Banks said Li then called her mother-in-law in China, who also was unsuccessful in reaching her son. The mother-in-law reached out to her daughter in the same Brooklyn neighborhood, Banks said.

She and her husband came to the house and banged on the door. When it opened, they faced a grisly sight: a man they didn't know, covered with blood. The couple called 911, and officers investigating another matter nearby responded quickly, Banks said.

"It's a scene you'll never forget," he said. The victims had wounds in their necks and torsos.

Chen was in custody and not immediately available to comment; it was not clear whether he had a lawyer. Banks said he had at first resisted arrest and, while being processed, assaulted a police officer.

Bob Madden, who lives nearby, was out walking his dog Saturday night when he saw a man being escorted from the two-family brick house by police. He was barefoot, wearing jeans, and "he was staring, he was expressionless," Madden said.

Yuan Gao, a cousin of the mother, came by the house Sunday and stood on the street, along with the neighborhood's mostly Chinese residents.

Some said that at Chen's latest temporary home, days before the brutal killings, late-night arguments were loud enough to be heard outside.

Gao said Chen was emotionally unstable. "He's crazy," she said.

Gao also said Chen kept getting fired from various restaurant jobs after only a few weeks.

Fire department spokesman Jim Long said emergency workers responded just before 11 p.m. to a 911 call from a person stabbed at the residence in Sunset Park, a working-class neighborhood.

Neighbor May Chan told the Daily News it was "heartbreaking" to learn of the deaths of children she often saw running around and playing.

"They run around by my garage playing. They run up and down screaming," Chan said.

Other neighbors said they had heard loud arguments emanating from the home late on several nights before the murders.