The shooting took place around 9:30 p.m. in the parking lot of the Union City BART station.
According to BART, one suspect was shot by police and transported to the hospital. Their condition is unknown, according to agency spokesperson Anna Duckworth.
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BART Police closed the station during the investigation.
"Per policy, BART's Office of the Independent Police Auditor has been notified and has responded to the scene for their investigation," the agency said.
BART will release more information as it becomes available, Duckworth said.