The shootings appear to have taken place after robberies or attempted robberies in the four stores, located in the cities of Riverside, Santa Ana, Brea and La Habra.
The national brand 7-Eleven celebrated its 95th anniversary during the day, which of course has the date 7/11.
The first shooting, at Riverside - where the victim was found in serious condition - has not yet been officially linked to the latter three, "although they all seem very, very similar" according to police Ryan Railsback.
The shooting in Riverside occurred just before 2 a.m. local time.
Railsback went on to comment on the shooters' potential connection to the special anniversary date:
"There is no chance this is a coincidence."
The second shooting occurred around 3:20 a.m., about 39 miles away in Santa Ana.
Investigators say the suspect in the Santa Ana murder is probably the same person who then traveled 19.31 kilometers to Brea, where a 7-Eleven employee was found dead from a gunshot wound shortly after 4 p.m.
Less than an hour later, police were alerted to the neighboring town of La Habra due to a robbery at another 7-Eleven.
Two people with gunshot wounds were found around 04.55.
The armed man had fled and no suspect has yet been found.
The store chain comments
"Our hearts go out to the victims and their loved ones," 7-Eleven, Inc. said in a statement, emphasizing that it is gathering information about the incident and cooperating with police.