File - In this June 2, 2020 file photo, journalist Ruhollah Zam speaks during his trial at the Revolutionary Court, in Tehran, Iran. Iran. Tranian state television and the state-run IRNA news agency say Ruhollah Zam was hanged early Saturday, Dec. 11, 2020, just months after he returned to Tehran under mysterious circumstances. (Ali Shirband/Mizan News Agency via AP, File)
Journalist Ruhollah Zam on trial at Tehran's Revolutionary Court. Mr Zam was executed yesterday. AP

Why is Iran killing journalists?