Eric Bellucci looked disheveled and disoriented during his court appearance Monday. Defense attorney John Kelly asked that Bellucci be placed on suicide watch as a precaution. He is being held without bail.
Assistant District Attorney Kirstin Mitchell said authorities recovered a bloody weapon in the defendant's bedroom. He lived with his parents.
Arthur and Marian Bellucci were found stabbed to death Wednesday night in their home.
Their son was picked up Friday at the Tel Aviv airport after trying to buy a plane ticket to Beijing. His confused manner alerted a flight clerk, who notified security officials.
New York City police said previously that Bellucci suffered from schizophrenia.