。
The late Mr. Smith was a doctor.
Literal
Passed-away Smith-Mr. [topic-は] doctor-[polite-past-でした]
亡くなる is the polite euphemism for 'to die' — lit. 'to become nonexistent'. Using the past form 亡くなった as a prenominal modifier on スミス氏 yields 'the late Mr. Smith'. 氏 (し) is a respectful suffix for adult men in formal contexts (news, obituaries, written records). The copula ~でした marks past tense + polite.