Terry Frei sent the tweet after Takuma Sato on Sunday became the first Japanese driver to win the race.
Frei sent a follow-up tweet apologizing to Sato and the paper for his comment, saying he "fouled up." He noted his tweet occurred during an emotional time when he was honoring his late father, who was a World War II pilot in the fight against Japan.
The Denver Post apologized on its website, saying that Frei's tweet was disrespectful and unacceptable. It said Frei was no longer employed and declined further comment.
Frei later tweeted a message apologizing saying that he "fouled up."
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