The man suspected of killing a reputed New York mob boss will remain in prison until his trial, within protective custody amid fears of Mafia retaliation.

Lawyers for Anthony Comello, 24, say hate speech and right-wing conspiracy websites are to blame for recent changes in his behavior.

Comello pleaded not guilty Monday as he was arraigned under heavy security on murder and other charges in the March 13 killing of reputed Gambino boss Francesco "Franky Boy" Cali.

According to authorities, the Staten Island slaying may have been related to a romantic dispute, not mob business.

At a court appearance last week, Comello had pro-Donald Trump slogans and an apparent conspiracy symbol on his hand.

Attorney Robert Gottlieb said Monday Comello's family attributes behavior changes to "hate spewed throughout the internet."

He's being held without bail.

His next hearing is April 3.