Saudi authorities said Monday that an Egyptian man was the second assailant in the weekend suicide bombing at a Shia mosque which killed four people and wounded 36 others.
The interior ministry identified the man who was overpowered by worshippers during Friday's attack as Talha Hisham Mohammed Abdo.
Witnesses had said he randomly shot at worshippers before he was disarmed.
The attacker who blew himself up at Al-Rida mosque in Eastern Province was identified Sunday by authorities as Saudi national Abdulrahman al-Tuwaijri.
So far there has been no claim for the attack, the latest in a series of assaults against members of the Shiite community in Sunni-ruled Saudi Arabia.
The Sunni extremist Islamic State group, which considers Shia heretics, has claimed responsibility for previous bombings and shootings.