(AP) - Looking dazed and speaking barely above a whisper, a Brooklyn hardware store clerk pleaded guilty Thursday to charges he abducted and dismembered an 8-year-old boy who lost his way home. The guilty plea to second-degree murder and kidnapping guarantees Levi Aron a sentence of 40 years to life in a case that traumatized the victim's tight-knit Orthodox Jewish community. Aron, 36, had previously pleaded not guilty to first-degree murder and, if convicted, would have faced life without parole. But the family of Leiby Kletzky urged prosecutors to strike a deal to avoid the painful spectacle of a trial. "There is no way one can comprehend or understand the pain of losing a child," the boy's father, Nachman Kletzky wrote in a statement distributed to the press. But he added that the plea gave the family "some partial closure on one aspect of this nightmare." Legal closure came Thursday afternoon after an expressionless Aron was led into the courtroom wearing an orange jail jump suit, handcuffs and a yarmulke. Judge Neil Firetog began by telling him that after seeing psychological reports, he was convinced claiming mental illness was "not a viable defense." The judge then had Aron answer a series of often leading questions about his conduct. His one-word responses were delivered in a low, flat monotone after long pauses and prodding by his lawyers. Aron expressed no remorse and only hinted at motive: At one point he told the judge he felt "panic" when he found out there was a frantic search on for the boy, who was still alive in his apartment. The judge asked him what he decided to do, and he responded simply, "Smother." He also answered yes when asked if he had bound and drugged Leiby. Afterward, defense attorney Jennifer McCann insisted that her client, though under medication, knew what he was doing. "He came here to accept responsibility for his actions," McCann said. "He understands the charges." The plea deal means Aron could technically qualify for a parole, but only if he survives in prison into his mid-70s.