DARBY, Pa. -

A doctor wounded by a patient in a deadly shooting at a hospital campus in Delaware County appears to have been the person who returned fire and wounded the suspect, authorities said.

The gunfire was reported around 2:30 p.m. Thursday on the top floor of Mercy Fitzgerald Hospital's wellness center, across from the hospital, at 1503 Lansdowne Ave. in Darby.

District Attorney Jack Whelan said investigators believe the doctor had his own gun and acted in self-defense.

Whelan said Richard Plotts, a patient with psychiatric problems, opened fire after entering the doctor's office with a caseworker Thursday afternoon.

The caseworker, Theresa Hunt, 53, of Philadelphia, was killed.

The doctor, Dr. Lee Silverman, appears to have suffered only a graze wound. Both he and the suspect were transported to a hospital in nearby Philadelphia.

Authorities have not publicly identified the two victims.

The 213-bed teaching hospital is part of the Mercy Health System, a large Catholic health care network serving the Delaware Valley.

The Sister Marie Lenahan Wellness Center is home to a wide range of outpatient services and physician offices.