The Gilgo Beach serial killer, Rex Heuermann, doesn’t sound like a model inmate … because he was reportedly caught with drugs and disciplined for smuggling a package into prison.

The convicted murderer allegedly tried to smuggle a package into the Clinton Correctional Facility in July and was later found with drugs … this according to disciplinary records obtained by The New York Post.

Unclear what was in the alleged package, or what specific drugs he allegedly had … but he’s set to face the music next week … there’s a Sept. 18 hearing scheduled.

As we reported … Heuermann pled guilty to several charges earlier this year in connection with the murders of 8 women on Long Island.

He was sentenced in June to three consecutive life terms in prison without the possibility of parole and 100 years to life. So he’ll be spending the rest of his days at Clinton Correctional Facility.