No doubt detailed claims of responsibility will soon emerge for the massacre of tourists in Sousse, Tunisia. Such attacks are far from unique, with examples of this tactic in north Africa going back to the 1990s, most notoriously at Luxor in Egypt in 1997.
Estimates of the importance of tourism to Tunisia are that it contributes as much as 15% of the nation's GDP. That presents a motivation to terrorist groups, but answers for their actions are also likely to be found within their political and religious belief systems. Past articulations indicate the tourist can be particularly 'provocative' to Islamists. This is Al-Gama'a al-Islamiyyah leader Talat Fuad Qasim in 1996 discussing tourists to Egypt:
"First, many tourist activities are forbidden, so this source of income for the state is forbidden. Striking at such an important source of income will be a major blow against the state. It does not cost us to strike against this sector. Second, tourism in its present form is an abomination: it is a means by which prostitution and AIDS are spread by Jewish women tourists, and it is a source of all manner of depravities, not to mention being a means of collecting information on the Islamic movement. For these reasons we believe that tourism is an abomination that must be destroyed. And it is one of our strategies for destroying the government."
Talat Fuad Qasim, quoted in "Religion and Political Violence: Sacred Protest in the Modern World" by Jennifer L Jefferis (Routledge, 2011, p.89).
We will see what statements emerge from the Tunisian attackers. But that mixture - of religious and economic imperative - may well be to the fore.