LARGO — A homeless man killed inside the Pinellas County Jail was not supposed to occupy the same cell with the inmate who ultimately choked him by shoving toilet paper down his throat, Sheriff Bob Gualtieri said Monday.

The error surfaced during an ongoing sheriff's investigation launched after authorities say Scott Alexander Greenberg, 28, killed Kelly Damon Harding, 48, early Sunday in the jail's Delta 6 pod, which houses felony inmates under protective custody.

When detainees arrive at the Pinellas County Jail, they are classified and placed in corresponding areas. Many will stay inside pods, which are secured rooms that include a common space for inmates and cells lining the walls.

Jail officials consider different factors when deciding where to house inmates, including gender and behavior. Sex offenders are also separated from the rest of the jail population.

Another factor: Inmates charged with felonies and those charged with misdemeanors are housed separately.

Greenberg, of St. Petersburg, was in jail on a second-degree murder charge — a felony — after an autopsy revealed he asphyxiated his girlfriend with toilet paper in August, according to records.

Harding was arrested in October on a burglary charge, which is also a felony. But in January, he pleaded guilty to a lesser charge of trespassing, a misdemeanor, and was sentenced to serve one year at the jail, records show.

After the sentencing, Harding was supposed to be relocated to live with other misdemeanor inmates. But his case number was not updated to reflect his change in status, Gualtieri said.

Days later when the inmate records section received the sentencing documents, Harding's misdemeanor status still was overlooked.

"Somebody just put it in his file without actually reading it and going into the system and changing his status," Gualtieri said. "Why was he still continuing to be housed with felons when he became a sentenced misdemeanor?"

Harding's interaction with felons at the jail had been limited. From November until last weekend, he had been housed in a single cell because of several behavioral issues, including defecating in the recreation yard.

The lack of single cells at the jail over the weekend was a factor in placing Harding and Greenberg in the same pod, Gualtieri said.

At the start of the weekend, both Harding and Greenberg were in single cells because of misconduct. But on Saturday, Harding was moved to the Delta 6 pod after jail staff determined another inmate needed to be in that single cell.

Greenberg was admitted to the jail clinic Saturday after falling in the shower and hitting his head. When he was released from the clinic Saturday night, a single cell wasn't available, so he also ended up in Delta 6.

Once secured inside the pod, Greenberg settled into an empty bunk in Harding's cell about 10 p.m. Saturday.

About three hours later, Harding was dead.

The pod is in the South Division, the oldest section of the jail. It does not have video surveillance. The idea of installing cameras in the division has been discussed before but could cost millions of dollars, the sheriff said.

Detention deputies check Delta 6 inmates every 30 minutes. The pod includes 16 cells furnished with one or two bunks. On Saturday night, 23 inmates were in the pod.

Greenberg attacked Harding just six minutes after a 12:52 a.m. check.

"He took a calculated risk," Gualtieri said.

At Hillsborough County jails, inmates with behavioral problems are not kept in pods but housed in single cells. The rest of the population — whether felony or misdemeanor inmates — are housed together, said Col. Ken Davis, who oversees the jails.

Both Greenberg and Harding are convicted felons with lengthy criminal records in Florida. Greenberg's convictions include interference in the custody of a minor and domestic battery. Harding has served at least six prison sentences since 1985 for charges that include burglary, cocaine possession and carrying a concealed firearm.

Greenberg is now isolated and under supervision in a single cell. He has been uncooperative with investigators and faces a first-degree murder charge in Harding's death.

He previously was held at the jail in lieu of $500,000 bail. But at a Monday afternoon hearing, Pinellas Judge Dorothy Vaccaro ordered him held without bail and appointed the Pinellas-Pasco Public Defender's Office to represent him on the new murder charge.

Authorities say Greenberg killed Harding shortly after telling some inmates he planned to be executed on death row rather than spend his life in prison.

Pinellas-Pasco Chief Assistant State Attorney Bruce Bartlett said his office will consider whether to seek the death penalty for Greenberg. One factor to be considered is that he is now charged with two murders.

Greenberg "seems to have an insatiable desire to hurt people," Bartlett said.

Times staff writer Curtis Krueger contributed to this report. Laura C. Morel can be reached at lmorel@tampabay.com or (727)445-4157.