Updated at 9:47 p.m. ET
A Chinese immigrant who neighbors said struggled to survive in America was arrested Sunday on five counts of murderin their Brooklyn home - using a butcher knife.
The suspect, restaurant worker 25-year-old Mingdong Chen, implicated himself in the killings late Saturday in the Sunset Park neighborhood, police said.
"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. Their brother, 5-year-old Kevin Zhuo, and 37-year-old mother, Qiao Zhen Li, were taken to hospitals, where they also were 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. He came to the United States from China in 2004 and seemingly struggled to make it, Banks said.
"Ever since he came to this country, everybody seems to be doing better than him," he said.
On Saturday night, Chen had apparently been acting in such a way that concerned Li, Banks said. She tried to call her husband, who wasn't home, but couldn't reach him.
Banks said Li called her mother-in-law in China, who also was unsuccessful in reaching her son. The mother-in-law reached out to her daughter, who lives in the neighborhood, Banks said.
She and her husband came to the house and banged on the door, then called police. Officers in the area investigating another matter responded, Banks said.
"It's a scene you'll never forget," he said. The victims had wounds in their necks and torsos.
Chen was set to undergo a psychiatric evaluation Sunday night, CBS New York reported. He also faces counts of assault on a police officer, which happened while he was being processed, and resisting arrest, Banks said.
Bob Madden, who lives nearby, was out walking his dog when he saw a man being escorted from the building by police. He was barefoot, wearing jeans, and "he was staring, he was expressionless," Madden said.
Yuan Gao, a cousin of the mother, said the man had recently moved to the area and had been staying with different people.
Fire department spokesman Jim Long said emergency workers responded just before 11 p.m. to an emergency call from a person stabbed at the residence in Sunset Park, a working-class neighborhood of adjoining two-story brick buildings with a large Chinese community.
A neighbor who gave his name as Larry told CBS New York he said the family's father return to the house after the killings.
"He was yelling that he was the father, and he ran into the house," Larry said.
Neighbors said they were stunned to learn about the slayings.
"It takes a real evil person to stab a child," Michael Chan told CBS New York. "I feel like stabbing anybody is like a very personal attack. And stabbing a kid is like a monster. Only a monster's capable of doing that."