Investigators say the two masked gunmen didn't say a word to customers before they opened fire.
One man died at the scene and six others were injured. Two victims were hospitalized in critical condition. Four others suffered wounds that were not considered life-threatening.
A motive for the shooting is under investigation, but police say it may be gang-related. The coffee house and the customers were not robbed.
The suspects are described as two males, possibly Asian, who were wearing bandanas to cover their faces. The suspects fled on foot and no vehicle was seen leaving the incident.
San Gabriel police were in the area of Valley and San Gabriel boulevards and heard the gun shots.
"At about that same time while they were investigating the origins they received a call from the Coffee House," said Lt. Pat Nelson from the L.A. County Sheriff's Department.
Police are asking for the public's help. Anyone with information is urged to call L.A. County Sheriff's homicide detectives at (323) 890-5500.
The Coffee House does have surveillance cameras, but it is unknown whether or not they were working at the time.
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