The man, named by local media as Jason Richard Stevens, 39, a Scottish translator, was killed in Sao Paulo on Wednesday.
It has been reported that one suspect was robbing customers while another guarded the door.
Mr Stevens attempted to speak to one of the two robbers, who then shot him.
The two assailants are then believed to have fled the scene in a getaway vehicle driven by a third man.
Mr Stevens was taken to hospital but died of his injuries. No-one has been arrested over the incident.
A Foreign and Commonwealth Office spokesman said: “We can confirm the death of a British national on 22 October in Brazil.
“We are offering consular assistance to the family at this difficult time.”