Thomas Ossel, from Bedfordshire, was fatally shot in the jaw while his brother Jack was wounded but survived.
The brothers were staying at a backpacker hostel on Margarita Island, one of the country’s leading tourist destinations. They had left a bar on Monday evening and were on their way home when they were confronted by robbers.
Investigators believe gunmen tried to rob the men and apparently opened fire when they resisted, according to Luis Garavin, a regional police official.
Jacqueline Baxter, a friend of the family, said: “At the moment their father has travelled to Venezuela and obviously their mum is not able to make a statement. The younger son is still out there, so he is still at considerable risk.”
In a recent internet posting Thomas Ossel, a firefighter, described how he had been to 40 countries and was hoping to reach 100. According to a social networking website he was 28, and his brother is 21.
Tributes poured into the social networking website Facebook. One friend said: “His humour is one of the amazing qualities that made him such a great guy.” Another said: “I still can’t believe that this has happened. I always imagined Tom growing old on a beach somewhere.”
A Foreign Office spokesman said it was providing consular assistance for the family.
The Foreign Office has warned that street crime in Venezuela is high, and that armed muggings and “express kidnappings” – opportunistic abductions to extort money – are regular occurrences.
Venezuela has one of the highest murder rates in Latin America. Last year, it reported a rate of 48 homicides for every 100,000 inhabitants.