(CNN) -- Psychiatrist Lee Silverman may have saved lives Thursday afternoon, when a patient opened fire in a suburban Philadelphia hospital.
Delaware County District Attorney Jack Whelan said the shooting happened around 2:30 p.m. in a treatment room at Mercy Fitzgerald Wellness Center in Darby, Pennsylvania, according to CNN affiliate KYW-TV.
Whelan said it appears an outpatient psychiatric patient shot and killed a caseworker before the doctor, who was carrying his own weapon, shot the patient. Authorities said they did not know why the patient opened fire.
Whelan identified the patient as Richard Plotts of Upper Darby, Pennsylvania, and the caseworker as Theresa Hunt of Pennsylvania.
Silverman was grazed by a bullet but otherwise not injured, Whelan said. Plotts was in critical condition at the Hospital of the University of Pennsylvania, the district attorney said.
Witnesses described a chaotic scene as numerous law enforcement officers descended on the hospital.
"The scene looked like a small army. It was very surreal, but it was comforting that if something happens this severe and we can come together," said Rohan Hepkins, mayor of nearby Yeadon, Pennsylvania.
"The police came in droves and they locked down everything. They chased everybody on the inside, and then we (saw) a SWAT team come in," a bystander told KYW.
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Posted by Greg Palmer