After an autopsy on Saturday, Ellen S. Borakove, a spokeswoman for the medical examiner’s office, said the cause of death was “blunt impact injuries of the head, torso and extremities with liver laceration and internal bleeding.”  A spokesman for the Administration for Children’s Services said the agency was looking into the matter, adding that the boy’s family did not appear to have had previous contact with the agency.  The death occurred days after officials at the child welfare agency acknowledged serious lapses in the case of a bruised and emaciated 4-year-old girl who was found dead in her mother’s apartment in Bedford-Stuyvesant on Sept. 2.  In the case of Aiyden, some neighbors said they had recently heard yelling and crying coming from his home.  Pamela Davis, 44, an aunt of Ms. Foster, wept on Saturday as she recalled last seeing the boy on Sept. 17. Ms. Davis said her niece did weekend security work at a union office in Upper Manhattan and would normally stay with her son at Ms. Davis’s apartment in Harlem from Friday to Sunday.  But on Friday, Ms. Foster called to say that her new boyfriend would watch Aiyden while she was at work, Ms. Davis said. At 4 p.m., Ms. Davis said she called Aiyden because he had not called her, as he normally did.  “Reggie says, ‘Oh, he’s all right,’ ” Ms. Davis said. “ ‘He’s sleeping.’ ”  When she later called the home, Ms. Davis said, Mr. Williams told her: “ ‘I’m sorry, P. I love you. I’m so sorry.’ ”  A version of this article appears in print on September 26, 2010, on Page A20 of the New York edition with the headline: Man Is Arrested in Death of Brooklyn Boy, 2. Order Reprints| Today's Paper|Subscribe
Aiyden Davis was unconscious and covered in bruises when paramedics found him in his mother’s apartment, and he was later pronounced dead at a hospital.