DARBY, Pa. -

A man who authorities said fatally shot a caseworker at a hospital complex in Delaware County and was then shot by his psychiatrist remains listed in critical condition.

Richard Plotts is expected to be arraigned on murder charges at his hospital bedside on Friday, according to a spokeswoman for the Delaware County district attorney's office

Authorities are trying to determine more about the relationship between Dr. Lee Silverman and Plotts, 49, including whether the doctor had reason to fear him and why he had a gun.

The shooting occurred Thursday afternoon at a wellness center at Mercy Fitzgerald Hospital in Darby. Silverman suffered a minor wound.

The hospital said its policy bars anyone but on-duty law enforcement officers from having a weapon on its campus.