'Lizzie McGuire' Dad Robert Carradine Died in Hospital

Robert Carradine -- the actor best known for his roles in "Lizzie McGuire," "Revenge of the Nerds," and "The Long Riders" -- died in a hospital ... TMZ has learned.

The Los Angeles County Medical Examiner revealed Robert's place of death in new documents obtained by TMZ ... but the docs don't include a cause or manner of death.

Robert died Monday, and his family said he took his own life after battling bipolar disorder for two decades.

The death shocked Hollywood ... but as we first told you, there were troubling signs on his final film project ... with one of his most recent colleagues telling us he went MIA from a film.

Hilary Duff played Robert's onscreen daughter in "Lizzie McGuire," and she said his death "hurts" and she's "deeply sad to learn Bobby was suffering."

He was 71.

RIP

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