Darwish, also known as Abu Omer Hassan, is currently serving as the head of Hamas' Shura Council, a position previously held by Osama al-Mazini before his removal in December.
Al-Mazini, a senior Hamas figure, was involved in the Gilad Shalit case and served as a minister in the Gaza government. Darwish's role is temporary until Hamas can hold elections next year.
Last week, the New York Times reported that over 24 people, including senior intelligence and military officers, were arrested by the Revolutionary Guards on suspicion of being involved in Haniyeh's assassination. Among those detained were senior officers from the Revolutionary Guards' intelligence branch and staff from the guest house where Haniyeh was staying.
The British Telegraph reported that the Mossad recruited Revolutionary Guards agents for the mission, who planted explosives about two months ago, following the helicopter crash that killed former Iranian President Ebrahim Raisi. The assassination attempt on Haniyeh was initially planned for his arrival at Raisi's funeral but was postponed. Mossad agents later planted explosives in three rooms at a guesthouse in northern Tehran, anticipating Haniyeh's stay there. After planting the explosives, the agents, believed to be from the VIP Protection Unit of the Revolutionary Guards, fled Iran but retained a source inside the country.