About ten people arrived at the busy store in the Las Torres neighborhood in a vehicle and two motorcycles, and opened fire with automatic weapons.
According to media reports three people were killed inside the store along with a 14 year-old boy who happened to be walking by. Three of six wounded customers who were rushed to a local hospital also died.
Police at the scene of the crime said they did not have a motive for the crime or an identity for the assailants.
This year more than 220 people have died in killings of three or more people, according to the figures.