Somerville (Mass.) PD's Det. Mario Oliveira was assigned to a federal task force when he was shot in the chest, after approaching a suspect wanted by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), reports the Boston Globe.

Det. Oliveira had located Matthew Krister, 21, and returned fire when Krister fired on the officer, striking him in the chest. Krister was pronounced dead, following the 6:40 p.m. Tuesday shooting.

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