PITTSBURGH — A man seen on a transit bus with one of two sisters who were found dead the next day has been identified by city police, who plan to interview him as a witness in the case.

Pittsburgh police Lt. Daniel Herrmann announced Tuesday that police had identified the man a day after publicizing photographs of him from surveillance videos taken aboard the Port Authority of Allegheny County transit bus on Feb. 6.

Police had said Monday the man could be a key witness in the slaying of Susan Wolfe, 44, and her sister, Sarah Wolfe, 38, who lived together in the city’s East Liberty section. Their sister, Mary Wolfe, is a Democratic state representative from Clinton, Iowa.

Police weren’t releasing the man’s name but think he may have information helpful to their investigation because he was on the bus with Susan Wolfe that evening. The sisters were found dead the next morning in the basement of the home they shared, each with a single gunshot wound to the head.

Police have said there was no sign of forced entry into the home and that Sarah Wolfe’s car was found parked a mile away but have otherwise declined to release details, saying the investigation remains too sensitive.

“It should be made clear that this male is not a suspect but merely a witness that could provide homicide detectives with essential information relevant to this investigation,” Herrmann said in a statement Tuesday.

Sarah Wolfe was a psychiatrist for the University of Pittsburgh Medical Center’s Western Psychiatric Institute and Clinic. Susan Wolfe had recently moved to the area to live with her sister and worked as a teacher’s aide at Hillel Academy in Pittsburgh’s Squirrel Hill neighborhood.

Hundreds of people attended a funeral service for the sisters Friday in eastern Iowa.