Saudi authorities informed the family of Hasan Zahiri, 16, on Saturday that he succumbed to injuries, the relatives said, raising the death toll of the attack on a house in the Shia village of Al-Awamiya to three.
Security forces had tracked down Khalid al-Labad to a house in Al-Awamiya, in the Qatif district, the interior ministry said on Wednesday. It said a gunbattle erupted when police attempted to arrest the man who figured on a list of 23 Shiites wanted in connection with unrest.
Labad and a comrade were shot dead, while "two of the gunmen with him were wounded and a third was arrested," the ministry said.
Since early 2011, mainly Shia towns in Eastern Province have seen sporadic protests and confrontations between police and marginalised Shiites who are estimated to number some two million in the Sunni-dominated kingdom.
Unrest erupted after an outbreak of violence between Shia pilgrims and religious police in the Muslim holy city of Medina in February 2011.
The protests escalated when the kingdom led a force of Gulf troops into neighbouring Bahrain the following month to help crush Shia-led pro-democracy protests against its Sunni-minority monarchy.
Human rights groups say more than 600 people have been arrested since spring 2011, most of them in Qatif. The majority have since been released.