で亡くなった

died of; died from

→ で
phrase Uncommon #8,919
died of; died from Attach で to the cause of death to say what someone died from. 亡くなった is a respectful way to say “died.”
JA: 彼は去年がんで亡くなった。
EN: He died of cancer last year.

新聞によれば、首相がガンで亡くなったそうです。

According to the newspaper, the prime minister reportedly died of cancer.

ジョンのお父さんが心臓発作で亡くなったのを知っていますか。

Did you know that John's father died of a heart attack?

トムはあの事故で亡くなったんですか?

Did Tom die in that accident?

彼は食べ過ぎで亡くなった。

He died from overeating.

トムは心臓発作で亡くなったんです。

Tom died of a heart attack.

彼は去年がんで亡くなった。

He died of cancer last year.