Upper Darby police had long suspected that the murder of 84-year-old Jane Morgan was not a random act of violence - that whoever raped, beat and strangled the helpless cat-lover was someone she knew.

Yesterday, aided by DNA evidence, they busted her neighbor, Billy Williams, a deli worker and supposed friend of Morgan's who they say murdered her, then positioned her body to make it appear as if she had died of natural causes.

He lives two floors below her place in the Long Lane Apartments.

"It was a violent death; it was a violent struggle," said Upper Darby Police Superintendent Michael Chitwood Sr., who described Williams, 61, as "an animal."

"Even animals don't kill for sexual gratification," he said.

Williams worked at a nearby delicatessen and would make trips to the bank and grocery store for Morgan and other elderly tenants, apartment officials said.

"That's as bad as it gets," Long Lane Apartments manager Louise Stromberg said, when told of Williams' arrest.

Williams, who police say has prior convictions for rape, burglary, arson and firearms violations, also has been charged with stealing from a second elderly woman there.

Stromberg was visibly relieved yesterday to hear that Williams had been removed from the 215-unit complex, where Morgan had lived for nearly four decades. But she said it was disturbing to know that he had remained free for nine months after the murder.

"Pretty freaking creepy," she said. "I am so relieved."

Morgan was found dead in September after a friend reported that he couldn't contact her. Police had not initially suspected foul play because she suffered from several medical conditions and appeared to have died in bed.

"We thought she had a heart attack," said Ted McGuigan, the maintenance worker who found Morgan's body.

Before police arrived that day, Williams mysteriously appeared at her door and asked, " 'Oh, is she all right?' " McGuigan said. "He tried to walk past me and I said, 'She's gone.' "

Williams, who is charged with murder, rape, burglary and related offenses, is being held without bail at the Delaware County prison.

Upper Darby Police Capt. George Rhoades Jr. said the assistance of forensic scientists at Philadelphia's DNA lab was crucial to solving the crime. Skin cells found under Morgan's fingernails - a sign that she had struggled for her life - matched Williams' DNA.

"She clawed to stay alive," Rhoades said.

Williams has confessed to "all aspects of the crime," he said, including the attempted cover-up.*