CHICAGO (CBS) — The reason for convicted wife killer Drew Peterson’s transfer from an Illinois prison to a federal facility in Indiana remained a mystery on Wednesday, but his attorney said whatever the basis might be, the former Bolingbrook police officer is “probably better off.”

Peterson, 63, recently was moved from the Menard Correctional Center in southern Illinois to the Stateville Northern Reception and Classification Center, which is used for processing prisoner transfers in Illinois. On Tuesday, he was transferred from state custody to the U.S. Bureau of Prisons, and taken to FCI Terre Haute, a medium-security prison in Indiana.

Peterson’s attorney, Steve Greenberg, said he was in the dark about the move until he saw news reports Tuesday afternoon.

“As a lawyer, we don’t want to say we’re clueless. I have no idea why they moved him,” Greenberg said. “Never have seen this before in my 30 years of doing this. Never.”

He said the move from a 140-year-old state facility with non-air-conditioned cells to federal prison in Indiana is actually a step up.

“For Drew, he’s probably better off in a federal facility,” he said.

CBS 2 Legal Analyst Irv Miller said there are several possible reasons for the transfer.

“His own security, they can’t protect him. Two, he’s a witness on a federal case that we don’t know about. Or three, he’s been indicted himself,” Miller said.

Greenberg said, as far as he knows, Peterson is not involved in any ongoing federal or state criminal cases.

“I checked yesterday with the U.S. attorney’s office. They said nothing was going on. I checked with Will County [State’s Attorney’s office], they said nothing ws going on. I don’t anticipate there’s any further prosecutions of him,” Greenberg said.

With no new charges filed against Peterson, and Greenberg insisting he’s not an informant on another case, some experts have speculated the former Bolingbrook sergeant was transferred to prevent him from being harmed or possibly killed in prison.

“I talked to him 10 days ago, and he didn’t tell me anything about being beaten,” Greenberg said.

Greenberg also said Peterson didn’t say anything about being threatened with bodily harm while in state custody.

In 2013, Peterson was sentenced to 38 years in prison for the murder of his third wife, Kathleen Savio. While in prison for that crime, he was convicted of trying to hire a fellow inmate to kill Will County State’s Attorney James Glasgow, and was sentenced to an additional 40 years in prison.

Peterson has been named a suspect in the disappearance of his fourth wife, Stacy Peterson, in 2007, but has not been charged in that case.

As authorities were investigating Stacy’s case, they also reopened the investigation into Savio’s death, which originally was ruled an accidental drowning. A new autopsy later ruled Savio’s death a homicide, and Peterson was convicted of her murder.

Peterson’s son, Stephen, recently revealed he believes his father “probably” killed both Kathleen Savio and Stacy Peterson.