Conner said he would not discuss the details of how the man died or the cause of death until the autopsy report is completed.
"The last time we can confirm anyone saw him was 1:20 a.m.," Warden John Wetzel said.
While the man was in a cell with one other inmate, Wetzel said it was a corrections officer who discovered the man with a bedsheet tied around his neck.
"Nobody woke up," Wetzel said of the approximately 20 other inmates on that cellblock.
Medical and correctional officers performed CPR on the man until the ambulance arrived, said Wetzel, the warden since 2002.
"He was someone we'd definitely classify as a special-needs inmate," the warden said. The man was not on a suicide watch, but was in a special-needs wing for inmates with diagnosed mental illnesses or in protective custody.
"It's a unit for inmates that require closer supervision," he said. Prisoners are checked every half-hour on the block, he said.
Wetzel said the man had been in jail on two separate sets of charges since March 25 and was awaiting trial. He had been charged with terroristic threats and harassment in one case and terroristic threats, impersonating a public servant and disorderly conduct in another, according to the warden.
"For pretty much the past year, this segment of our population has increased - and it's not just here, but nationwide," Wetzel said of prisoners with mental illnesses. He said the national figure is 17 percent to 20 percent, about the same as in the county prison, the warden said.
While Conner did not rule on the cause of death Sunday, Wetzel said the last inmate suicide was a hanging in October 2001.
Counseling was made available to staff and inmates, Wetzel said. While it appears that all procedures were properly followed, he said there will be thorough internal and external investigations into the incident.