Two people were killed and several others were injured in four shootings at 7-Eleven convenience stores across southern California.

Authorities say that the violence unfolded across the region in the early hours of Monday morning, which also happens to be the company’s national 7/11 Day, when customers get a free slurpee drink.

Police say that they believe three of the shootings, in the cities of Brea, La Habra, and Santa Ana, are linked and have released a surveillance photo of the suspect they are looking for.

And they say they will be telling other 7-Eleven stores in the area to take additional security precautions in the wake of the shootings.

A male store clerk was shot and killed at the store in Brea at around 4.18am, according to investigators.

Police say that at a store in the city of La Habra, an employee and a man sitting outside in his car were also shot at around 4.55am. Officials say that both men are expected to survive the attack.

An hour earlier, a similar incident took place at the Santa Ana store where a male victim was found in a car park with a fatal gunshot wound to the torso.

A customer was shot in the head during an armed robbery at a 7-Eleven store in Riverside, California, at around 2am.

Officials say that the victim did nothing to intervene in the robbery but was still shot and remains in grave condition.

Police say there is no evidence yet to link the shootings in Riverside to the other three.