The Tunisia gunman was part of a five-man terror cell in existence for the last four years.
Seifeddine Rezgui was a long-term jihadist and an Islamic State (IS) 'sleeper' who loved everything it stood for, according to his friend at Kairouan university - Sky News reports.
Fellow student Wassim Bel-a-Del told Sky that the attack was co-ordinated by IS and that Rezgui was trained by the group in Libya.
"In 2011 he was with Al Nusra," he said. "Then when Daesh (IS) started in Syria and Iraq he changed his allegiance and supported Daesh, and he loved everything they stood for.
"I know the group he is working with; it is a group of terrorists. There are some guys who go to Syria and come back and go on to study in the same university, and there are others who go and die in Syria."
Mr Bel-a-Del said Rezgui told him he was part of IS and he is in no doubt his friend received training from IS commanders in Libya. He believes Rezgui was a 'sleeper', a terrorist ordered to lie low until activated by his handlers to carry out an attack.
"He was training in Libya because the terrorist groups find it easy to go to Libya," he said. "They will train there and they will come back without any problem from the police.
"Their commanders are there in Libya; they have a base and Ansar Sharia support Daesh and this is why they have the best place to go into Libya and come back without any problem.
"I am sure the commander told him to disguise himself from the other students, to say 'he's not a dangerous terrorist or from a terror group'. It's a cell system where no group knows what another group is doing. It is just the bosses that connect them."
Seven suspected associates of Rezgui arrested in three different cities are being questioned in the capital, Tunis.
The Tunisian authorities have said he acted alone during the attack but that accomplices provided him with weapons and logistical support.
Some 17 victims from Britain and three from Ireland have been identified.
Sky report that as many as 30 UK nationals were killed when Rezgui opened fire on tourists in the resort of Sousse.
