NAPERVILLE (STMW) – The brother of a Naperville woman found beaten to death Wednesday night in her home has been identified by police as a “person of interest” in that crime.

Mark R. Lewis, 51, of Lakemoor, has not been seen or heard from in days by relatives and friends. His older sister, Cathleen A. Lewis, was found slain in her Naperville townhome.

“Recent developments into the murder investigation … have brought the [Naperville] Police Department to focus on a person of interest,” Naperville police Sgt. Gregg Bell said Friday evening in a prepared statement.

Authorities believe Mark Lewis “was involved in identity theft and forgery of his mother’s bank account,” Bell said. He did not provide details of that alleged crime.

Police have obtained a warrant for Lewis’ arrest for identity theft, Bell said.

Bell’s statement reflected a marked change in tone in the case. Bell on Thursday released photographs of Lewis and the rear of his green, 1999 Ford Explorer bearing Illinois license plate number 775 8696.

Thursday’s release, however, stated police “would like to confirm Mr. Lewis is OK, and to notify him of his sister’s death.”

Cathleen Lewis, 59, died of severe head injuries apparently inflicted inside her townhome in the 2300 block of Worthing Drive in Naperville. The gray-colored, eight-unit building is located near Naperville’s Old Farm/Old Saw Mill neighborhood.

Bell on Thursday confirmed police found no sign of forced entry into the home, which Lewis shared with her elderly mother. He said Cathleen Lewis likely knew her killer and voluntarily let him or her inside the townhome.

Police went to the scene Wednesday evening to perform a “well-being check” at Lewis’ home. Lewis’ mother, reportedly in her 80s, was not home at the time, and called police from an undisclosed location to report she had been unable to contact her daughter.

An audio news release issued by the Will County coroner’s office said Lewis was pronounced dead at 7:47 p.m. Wednesday. An autopsy performed Thursday concluded she sustained “multiple head injuries … due to assault,” according to that statement.

Funeral arrangements for Lewis are being coordinated by Friedrich-Jones Funeral Home in Naperville. A Friedrich-Jones spokesman on Friday would not provide details of the services, saying the funeral would be private.

Lewis’ murder is Naperville’s first in nearly three years, since Michael J. Fairbanks, 18, was fatally stabbed Nov. 26, 2008, during a drug-related argument near Keats Avenue and Falkner Drive.

A Bolingbrook man, Cortez R. Branch, 23, has been convicted of second-degree murder in that case and is awaiting sentencing.

Anyone with information about Lewis’ murder or the whereabouts of Mark Lewis are asked to contact Naperville police at 630-420-6147.

Those who want to remain anonymous may call Naperville Crime Stoppers at 630-420-6006. A reward of up to $1,000.00 is being offered for information leading to an arrest in the slaying.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2010. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)