DARBY, Pa. — Authorities are attempting to determine why a patient fatally shot a caseworker at a hospital complex in a Philadelphia suburb and whether a psychiatrist who pulled out his own gun and wounded the patient had concerns about him.

The psychiatrist, Dr. Lee Silverman, was grazed in the temple during the gunfight in his office Thursday afternoon with patient Richard Plotts, Delaware County District Attorney Jack Whelan said.

“We do believe that there were some issues between the doctor and the patient, but whether or not he actually feared him is unclear,” Whelan said.

The prosecutor identified the caseworker killed at Mercy Fitzgerald Hospital as Theresa Hunt, 53, of Philadelphia. Hunt had accompanied Plotts to an appointment with Silverman at a psychiatric crisis center adjacent to the hospital in Darby, just southwest of Philadelphia, authorities said.

“When the caseworker was shot, (Silverman) crouched down behind the desk to avoid him being shot,” Whelan said. “He was able to reach for his weapon, and realizing it was a life or death situation, was able to engage the defendant in the exchange of gunfire.”

A struggle ensued and spilled out into the hallway, Whelan said. Another doctor and a caseworker jumped in to help Silverman and secure Plotts’ weapon, he said.

The motive for the shooting remained unclear. Whelan said Plotts, of Upper Darby, might have had issues with the doctor over his treatment plan. It is not known, however, if that is why Silverman was armed, apparently against hospital policy.

Whelan said Plotts, 49, underwent surgery Thursday night at the Hospital of the University of Pennsylvania. Silverman was treated and released. Telephone calls to the doctor’s home went unanswered.