Rex Heuermann, the Manhattan architect who pleaded guilty to a series of murders that earned him the Gilgo Beach killer label, lives in near-total isolation at the Suffolk County Correctional Facility in Riverhead, New York, Sheriff Errol Toulon said in an interview with the Associated Press.

Toulon said Heuermann, 62, occupies a segregated cell and has not mixed with the general jail population since his arrest three years ago. His main diversion is reading crime novels — a genre with obvious parallels to his own crimes — by authors such as Heather Graham, John Sandford, Sue Grafton, and Lisa Jackson.

“He reads crime novels,” Toulon said.

The sheriff also disclosed an unusual piece of jailhouse correspondence. Keith Hunter Jesperson, the Oregon inmate known as the “Happy Face Killer” for the smiley faces he drew on letters to law enforcement, reached out to Heuermann. Jesperson, serving multiple life sentences for killing eight women across the country in the 1990s, wrote the first letter. Heuermann wrote back once but did not reply to several subsequent missives, according to Toulon.

Heuermann’s sentencing is scheduled for Wednesday. He pleaded guilty earlier this year to multiple murders in the Long Island case that began with the discovery of remains along Gilgo Beach in 2010. The jail’s security arrangements and Heuermann’s daily routine have been kept largely confidential. Toulon’s remarks offer the most detailed public account of the convicted killer’s life inside since his arrest.