There’s new information that Officer Michael Maes, the BART officer who shot and killed a fellow officer earlier this week, thought his victim, Sergeant Tom Smith, was an armed suspect.

According to the San Francisco Chronicle, unnamed sources familiar with the investigation said Maes did not accidentally fire his gun. They insist a split-second misjudgement by the officer led to the tragedy.

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Maes, Smith and another plain clothes detective were searching a Dublin apartment Tuesday in connection with a robbery arrest when the shooting happened.

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Investigators told the Chronicle the apartment’s layout led to confusion among the officers who became separated during the search.

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BART has not returned KCBS’ call to comment on the story. A spokesman for the Alameda County Sheriff’s Office tells the Bay Area News Group the Chronicle report is “inaccurate”… but declined to offer any details.