A 40-year-old worker fell to his death yesterday after he went to the roof of a four-story condominium project Downtown and slipped on its rain-slickened surface, city police said.

The victim, identified as Scott Oswald, was working at the Keystone Lofts in the 900 block of Liberty Avenue when he fell just before 8 a.m., police and the Allegheny County medical examiner's office said. Mr. Oswald was pronounced dead at Allegheny General Hospital at 8:49 a.m. An autopsy was planned.

"This gentleman was doing interior work when he decided to go to the roof to check on a prior job he had done," said city police Sgt. Robert Miller. "While he was up checking out the roof, with all the rain we had last night, he slipped and fell."

Jean Fitzgibbons, 22, of Lawrenceville, was on her way to work Downtown when she saw the man lying in Exchange Way, an alley behind the building. She said firefighters were soon on the scene.

"I saw him lying there and them doing what looked like CPR," she said.

Marcia Rodriguez-Kraus, a Howard Hanna agent and one of the sales representatives for the Keystone Lofts site, said the building, which will have a dozen loft condominiums, is under construction.