After American soil had covered his family's coffins, Yilin Zhuo had nothing left to stay for. In early December, he abandoned his adopted home, Brooklyn, for the Chinese village he had come from two decades ago.

"A father just wants to see his children grow up," he said, hours before his flight. "Now my children are gone. My wife is gone. Can I ever be happy again?"

Linda was 9; Amy, 7; Kevin, 5; and William, just 1. They and their mother, Qiaozhen Li, 37, were found stabbed to death in late October in their Sunset Park apartment. A cousin who had been staying with the family was arrested after the police found him there, his clothes spattered with blood, a large kitchen knife nearby.

It was family violence on a scale rarely seen in New York City, set in motion, the cousin told the police, by his sense of failure to find the security, stability and family all newcomers to Brooklyn's Chinatown seek.

Until that Saturday night, the household had been one more poor immigrant family among the thousands who have emptied the towns and villages around Fuzhou, in the Fujian Province in southeastern China, for Sunset Park.

Once in New York, the men board buses for jobs in the Chinese takeout shops and buffets that sprout improbably along neon-lit highways and inside small-town strip malls: west to Michigan, north to Maine, south to Georgia. America's Chinese restaurants are a diaspora of the Fuzhounese, nearly half a million of them hoping, like generations of immigrants before them, that long hours and low wages will someday make their uprooting worth it.

Mr. Zhuo, 41, was one such worker. His cousin, Mindong Chen, 25, was another. Their divergent paths — one on the way up, the other now charged with murder — lay bare the reality of life in this Chinese community: crushing burdens and relentless poverty, permanent for all but a few.

Mr. Chen's troubles were there for all to see in his postings on Qzone, a Chinese social media service. "Why is the pressure now so great?" he wrote. "The path has been so difficult."

Little has been told beyond the Chinese press about the people who died and about Mr. Zhuo, the father left behind, and Mr. Chen, the cousin. He is awaiting a hearing on whether he is mentally competent to stand trial for murder.

Both cousins had come to New York the same way, as young men sent away from home to grind away at busboy and wok-cook jobs that offer only the merest hope of a better life. But Mr. Zhuo built his chance into a humble career, home and family.

What little he had, his cousin — struggling, envious, desperate — is accused of shattering in one night.

Fired from yet another job and on the verge of deportation, Mr. Chen came to stay in the family's 57th Street apartment in October. He gambled. He smoked. He did not act right, Ms. Li told relatives. Days before the stabbings, Mr. Chen had argued with the children. The night of Oct. 26, Ms. Li, in a call with her mother-in-law in China, told her that Mr. Chen had a knife. By the time concerned relatives came to her door and Mr. Zhuo rushed home from work, it was too late.

Soon after his arrest, Mr. Chen told detectives that "everyone seems to be doing better than him" since he arrived in the United States in 2004, according to the police.

His family, and Mr. Zhuo's, had borrowed tens of thousands of dollars from relatives and friends for Chinese smuggling rings, known as snakeheads, to sneak their sons into New York City.

They would speak no English, have few prospects. But there was still a chance — to support their families, repay their smuggling debts, sponsor emigrating relatives and start families.

The restaurant workers live by two dark jokes. One plays on the Chinese words for snakehead, stove burner and pillow, which all end in the suffix meaning "head." "We Fujianese have three heads — snakehead, stove burner, pillow," they say. Arrive by boat or plane, cook, sleep, wake to cook again. Jobs last between a few weeks and a few years.