The suspect in the grisly killing of an 8-year old Brooklyn boy was arraigned on charges of murder and kidnapping in the first degree Thursday as law enforcement officials revealed more details of the gruesome slaying.

Levi Aron, 35, is accused of killing Lieby Kletzky after abducting the boy from a Borough Park street on his way home from camp.

Aron pleaded not guilty to the charges.

In court Thursday, Aron appeared pale and stared at the floor. Aron's lawyer said that his client has had hallucinations. He was remanded in custody and will undergo a psychiatric evaluation. Aron's attorney asked for his client to be put on suicide watch and in protective custody.

Outside Brooklyn court, Aron’s lawyers, Pierre Bazile and Gerard Marrone declined to comment on hallucinations and voices they said their client had heard. They would only say Aron’s demeanor was “not good,” and expressed their condolences to the Kletzky family.

Aron had scratch marks on his arm, a sign there may have been a struggle, Police Commissioner Ray Kelly said Thursday. Kelly said Aron has denied sexually molesting Leiby and, so far, no evidence suggests otherwise.

Earlier, Aron gave a written confession to police that stated "I understand this may be wrong, and I'm sorry for the hurt that I have caused," Kelly said.

Some of the boy's remains were found in Aron's Borough Park home early Wednesday.

The medical examiner believed the boy had been smothered or suffocated. Aron told police he had smothered the boy with a towel.

Aron reportedly told police that he brought the boy to a wedding in Monsey, New York, Monday night, but Kelly said investigators aren't sure Kletzky was with him. 

Brooklyn District Attorney Charles Hynes said police are interviewing attendees from the wedding.

Mayor Michael Bloomberg said he spoke to Leiby's rabbi Wednesday and to the child's mother and father on Thursday.

"It's every parent's nightmare, I suppose if there's any comfort to be taken, this is a once in a generation thing, the last time this happened was 30 years ago, but that's not any comfort to the parents," Bloomberg said, referring to the case of 6-year-old Etan Patz, who disappeared after leaving his family's apartment in Soho to catch a bus two blocks away. The case brought national attention to cases of child abduction, but unlike Leiby's case, Etan's body was never found.

With reporting by Ailsa Chang, Kathleen Horan, Beth Fertig, Stephen Nessen and the Associated Press