Four police officers were shot dead and another was wounded in the northern Californian city of Oakland on Saturday.
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Four police officers shot dead
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Officer involved in deadly shooting
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Police investigate shootings
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Officer shoots, kills dog
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Firefighter, police officer killed
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Police investigate 4 shootings in 4 hours
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Man shot by police during dispute
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Shots fired at officers
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Four Oakland police officers hospitalized after two patrol cars collide
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Berkeley police shoot, injure suspect who opened fire on them
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Police investigated after shots heard
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Police shoot man to death
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Officer killed in ambush, sets off manhunt
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Officer shoots officer;
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Senior Iraqi police officer shot dead in Baghdad
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Police shoot man dead
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Man shot by police expected to survive