Three people have been shot at a Delaware County hospital Thursday afternoon, the county District Attorney's office said, and one of those shot has died.

The fatally shot victim was a female employee of the hospital's wellness center in Darby Borough, Delaware County District Attorney Jack Whelan said. The second victim, a 52-year-old doctor, suffered a graze wound.

The suspect is in critical condition after being shot and detained at the hospital Thursday afternoon. Whelan said investigators were looking into reports that the doctor, who witnesses say is a psychiatrist, shot the assailant with his own gun.

"We're not sure exactly what happened," he said.

The suspect is a 49-year-old man and was taken into custody 10 minutes after the shooting, a police source told the Daily News' Stephanie Farr.

No names have been released, but Whelan said the suspect was a patient with a history of psychiatric problems.

The shooting took place at 2:30 p.m. on the third floor of the building, Whelan said. Police quickly responded to the Lansdowne Avenue hospital, and the three-story wellness center was evacuated and placed in a lockdown.

There were no other reported injuries.

The building contains offices for outpatient services, including pediatrics, cardiology, pulmonary care and psychiatrics.

Alfred Williams had just left a doctor's appointment and was waiting for a ride home when, suddenly, swarms of police officers descended on the scene.

"They kept coming," Williams said. "Guys with helmets and automatic weapons kept jumping out of their cars. It was total panic. ... I saw three people come out in stretchers." reporter Alex Wigglesworth contributed to this report.