Leiby Kletzky got lost leaving day camp and asked a man, Levi Aron, for help, police said. Detectives later found the boy's severed feet, wrapped in plastic, in Aron's freezer, as well as a cutting board and three bloody carving knives.
Aron has pleaded not guilty to charges of murder and kidnapping.
Leiby's death was officially ruled a homicide. It was caused by intoxication from the combined effects of cyclobenzaprine, a muscle relaxant; quetiapine, an antipsychotic; and the pain medications hydrocodone and acetaminophen, followed by smothering.
Prosecutors allege Aron lured Kletzky into his home on July 11. Video cameras captured the fateful encounter between the two on a Brooklyn street as Leiby's mother waited anxiously just a few blocks away.
Police and prosecutors said Aron, a clerk at a hardware supply store, has confessed to suffocating the boy with a bath towel, but they continued to work on verifying his horrific and bizarre explanation for the boy's death.
Police Commissioner Raymond Kelly said Aron told investigators that he brought the child to a suburban wedding about 35 miles away and spent several hours there. Other wedding guests confirmed Aron was there but didn't see the boy.
By the time the pair returned to the city, it was so late that Aron decided to take Leiby to his home to sleep and left him there Tuesday while he went to work, according to the police version of the confession. Kelly said the store confirmed that Aron showed up as usual that day.
Aron told police he killed Leiby when he got home after being spooked by a massive search for the boy in Borough Park section of Brooklyn, home to one of the world's largest communities of Orthodox Jews outside of Israel.
"When I saw the fliers, I panicked and was afraid," Aron said, according to police.
Investigators also have said Leiby may have been tied up and tried to fight back. Kelly said Aron had scratches on his arms, wrists and elsewhere -- a sign "there was some kind of struggle." There also were marks on the boy's remains that could have been caused by restraints, the commissioner added.