A psychiatric patient shot and killed a case worker and wounded a doctor at a wellness center in the Philadelphia suburbs on Thursday, officials said. Investigators believe the suspect was then shot several times by the doctor in a room at the Sister Marie Lenahan Wellness Center, which is on the Mercy Fitzgerald Hospital campus in Darby, Penn.

Delaware County District Attorney Jack Whelan told reporters that one female hospital employee died in the mid-afternoon shooting. The doctor was “grazed” in the head by a bullet, he added.

Whelan identified the suspect as Richard Plotts, a patient, and described him as having “psychiatric issues.” Officials haven’t identified either of the victims.

Officials believe the injured doctor shot the suspect three times after the suspect opened fire, Whelan said. The suspect was reportedly subdued by other employees of the hospital until police arrived.

“A worker did confirm that he heard some loud arguing going on,” Whelan said, according to NBC Philadelphia. “They came in and they actually opened the door and saw him pointing a gun at the doctor. They did not notice the case worker at that point. They shut the door very quietly and one immediately called 911.”

Then, Whelan said, shots rang out. The case worker was fatally wounded. The doctor was injured but returned fire with his own weapon, according to NBC Philadelphia, which cited a preliminary investigation and added:

Plotts has had run-ins with the doctor’s and hospital staff in the past, Whelan said. …

“We’re not exactly sure what had occurred and what might have precipitated this particular incident,” Whelan said. “We do know the psychiatric connection, we have that concern, however we don’t know if there was another dispute that occurred inside that room that led to these shots being fired.”

The local Fox affiliate and Philadelphia’s ABC station reported that the suspect was taken into custody soon after the shooting.

The Darby Borough Police Chief was not available for immediate comment, but Whelan told reporters that the suspect was being treated for at least one gunshot wound in his “torso area” and was in critical condition.

The scene was secured, and is no longer considered an active shooter situation.

Two people were injured and a caseworker killed at Pennsylvania's Mercy Fitzgerald Hospital on Thursday. Police have one person in custody, but the motive for the shooting is unknown. (Reuters)

[This post has been updated multiple times.]