The two Germans escaped unharmed in the January 13 incident in Awamiya village, Eastern Province.
At the time, the German government said it had no reason to believe the attack was politically motivated.
Saudi Arabia's interior ministry said the suspect, Salem bin Abdullah bin Hussein, was wanted for a number of crimes, including shooting, armed robbery and threatening the security of residents
He was arrested in Awamiya Thursday evening after a gun battle with police in which he was wounded and subsequently hospitalised. His two companions were also taken into custody.
On March 23, Saudi Arabia said it had arrested two other suspects in connection with the January shooting.
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Awamiya, just west of Dammam city, has been a focus of clashes between security forces and protesters from Saudi Arabia's Shiite Muslim minority.
Most Shiites live in the oil-rich east, and many complain of marginalisation in the Sunni-dominated kingdom.
Earlier this month, a court sentenced to death a man who opened fire numerous times on police in Awamiya.
Activists say several death sentences have been handed down since 2011, when demonstrations began among the minority Shiites.
In October, protesters marched there in opposition to death sentences handed to Shiite religious leader Nimr al-Nimr and others, an activist said.
Nimr was a driving force behind demonstrations against the Sunni authorities that erupted in 2011 in the east, alongside a Shiite-led protest movement in neighbouring Bahrain.