Tunisian student Seifeddine Rezgui opened fire on a tourist beach leaving at least 38 people dead. But the people who knew him told the BBC he was polite, never swore, never fought and liked breakdancing.
In the midday sun, Seifeddine Rezgui pulled a Kalashnikov from a parasol and opened fire on the beach, sending holidaymakers fleeing for their lives. He threw explosives at the pool area before continuing inside the Imperial Marhaba hotel.
Rezgui was not previously known to the security services. But Islamic State (IS), which said it was behind the attack, referred to him by a nom de guerre - Abu Yahya al-Qayrawani.
Unlike many Tunisian radicals, he is not believed to have gone to Syria or Iraq to join militants fighting there.
Tunisia's Interior Minister Najem Gharsalli said on Monday that officials are still trying to find out if he had attended a training camp in Libya, according to Reuters news agency.
His neighbours say they never saw him wearing conservative Islamic dress.
Social media accounts thought to belong to Rezgui had postings about rap music and the Real Madrid football team, but also posts in support of IS, as well as several of their propaganda videos, UK newspaper the Telegraph reports.
His last post on Facebook said Muslims should not celebrate New Year's Eve, according to Conor McCormick-Cavanagh, co-ordinator of the American Corner cultural centre in Tunis, who told the New York Times he viewed the page before it was taken down.
Mr McCormick-Cavanagh told the newspaper it was surprising that Rezgui had posted openly and publicly about his support for Islamic State and had gone unnoticed.
He grew up in his grandfather's house in Gaafour in Tunisia's interior. His family say they did not know about his Islamist beliefs.
His grandfather, Mohammed Ben Sghaier, told the BBC that he never skipped school and was never rude.
Similarly, Mohammed Ferchichi, who used to breakdance with Rezgui, said his friend never swore or fought on the street. Instead, Mr Ferchichi describes him as funny.
"He was just a normal guy like us but the terrorism took him," Mr Ferchini told the BBC.
A neighbour also described him as always polite.
He was studying electronics in Kairouan, one of the oldest Islamic centres in the world, when he is said to have drifted into extremism.
Rezgui shared a flat with four young men a few doors down from a mosque.
But the BBC was told this mosque was too moderate for his liking. Instead he travelled to a poorer district to attend a mosque where a more extreme version of Islam was preached.
Rauf Alsaaidy, assistant secretary-general of the General Union of Tunisian Students at Sfax University, has told the Telegraph that Rezgui was studious until he joined another Islamic student union with strong ties to the Muslim Brotherhood.
According to Mr Alsaaidy, he got involved in an Islamist campaign at the student union elections and also used to preach in front of the university.