Spokesman Hazem Qassem said on Tuesday that Imad al-Alami had been unconscious since the Jan. 9 shooting.
Hamas initially hastily announced al-Alami died naturally but later said he shot himself while checking his weapon at his Gaza City home and was in critical condition.
The 62-year-old al-Alami held several key posts as a member of Hamas’ policy-making body and lived in Syria before returning to Gaza in 2012. He remained a prominent official though not a member of the current politburo.
After the 2014 Israel-Hamas war, he traveled to Turkey for treatment for an injury in which he lost a leg. Hamas said he was wounded in the war.