BETHESDA, Md. (AP) — An FBI agent shot and wounded someone aboard a DC metro train in a Maryland suburb of Washington, D.C., on Tuesday, the agency said.

The shooting happened around 7 a.m. aboard a Washington Metropolitan Area Transit Authority train near the Medical Center station in Bethesda, Maryland.

The person who was shot was taken to the hospital for treatment, the FBI said. It was unclear exactly what prompted the agent to open fire.

Metro spokesperson Ian Jannetta said the agency’s transit police force was also investigating the circumstances surrounding the shooting.

In a statement, the FBI said it “takes all shooting incidents involving our agents seriously” and that an internal investigation has been launched, in line with standard bureau policy.

“The review process is thorough and objective and is conducted as expeditiously as possible under the circumstances,” the FBI said.

Metro said trains were sharing a track and bypassing the Medical Center station while the shooting is investigated. The station serves the National Institutes of Health and Walter Reed National Military Medical Center.

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