This video, filmed inside the Imam Rida Mosque in Mahasen, al-Ahsa shows the chaotic moments after a gunman opened fire on Shia worshippers during Friday prayers.
The footage was captured following a coordinated gun and suicide bomb attack on the mosque in south-east Saudi Arabia. Two or three were killed and seven injured in the assault, the Associated Press reported amid conflicting official statements.
The gulf kingdom's Shia minority has been the focus of a series of attacks by the Islamic State, although no individual group has claimed responsibility for this latest attack.
A number of other videos also posted on social media have also shown scenes of chaos in the al-Ahsa governorate in the immediate aftermath of the attack. One clip shows angry worshippers attacking one of the suicide bombers before he was able to detonate his device.
A later video shows security forces firing into the air to disperse crowds as they attempt to take hold of the attacker.