BEIRUT, Lebanon — The image of the Saudi crown prince shaking the hand of a son of the slain journalist Jamal Khashoggi stoked outrage on social media on Wednesday as suspicions continue that the crown prince had a role in the killing.

Many Turkish and American officials believe that the operation that ended up killing Mr. Khashoggi could not have gone ahead without the knowledge of the Saudi crown prince, Mohammed bin Salman.

Mr. Khashoggi’s son Salah is a dual Saudi-American citizen and has been barred from leaving the kingdom, friends of the family say, presumably to keep his relatives who are already in the United States from speaking out about the killing.