Police said Chen stabbed and slashed the victims in their necks and torsos. The family was found in various rooms in their apartment on the first floor of a two-story brick house. Some were hospitalized and pronounced dead; others died at the scene.
"It's a scene you'll never forget,'' said Chief of Department Philip Banks III.
Chen had been staying with the family for about a week. He was a transient and illegally in the United States, Assistant District Attorney Mark Hale said. An immigration hold was also placed on him.
Police said Chen apparently was envious of fellow immigrants' successes in America.
"He made a very soft comment that since he came to this country, everybody seems to be doing better than him,'' Banks said Sunday.
Chen was unemployed after being fired from a string of restaurant jobs he held for just a few weeks at a time, according to neighbors and relatives in the working-class Brooklyn neighbourhood dominated by a large community of immigrants from China.
The children's father, Chen's cousin, was not home late Saturday evening; he was working at a Long Island restaurant, one neighbour said. The mother tried to call him because she was alarmed about Chen's behavior earlier in the evening, police said.
Neighbours and relatives said the father was distraught over the deaths.
- AP